Read the sorry story of the financing of the domed stadium in downtown Toronto. Cost? $570 million in 1989. Purchased by Rogers Communications in 2004 after a series of buyouts and at least one bankruptcy: $25 million.
We also hate football 
Zimbalist (the guy I linked to) makes the point that they don’t really “bring in” money to the community – they shift around where already-present local money gets spent (and taxed) within the community. I.e., other than a large one-off where a big number of out of town fans descend on the town and drop big change at the hotels and restaurants (basically, the once a year bowl game scenario), the attendance and spending at a given NFL or NBA game is almost entirely made up of local fans (how many people travel from Milwaukee to Phoenix to watch the Bucks road game?), so there is not really a net influx of money.
Then there is the question of where, exactly, to build this new stadium. Nobody has ever floated anything even remotely acceptable. Irwindale? Not going to happen. If it isn’t in the center of LA, then forget it.
eta: What YogSosoth said, too. 
Here Here!
Well… yeah. They don’t.
Here’s a very recent item on this matter:
http://latimesblogs.latimes.com/lanow/2009/01/voters-in-indus.html
City of industry approved a bond issue. Note that City of Industry has fewer than 800 residents and 2500 businesses. It looks like something is getting “railroaded” that otherwise would not survive a vote of a larger and more diverse electorate.
Also, although the Yankees and Mets stadiums got approved (on false premises) in New York City, the West Side Stadium project for the Jets raised so much resistance that it turned into a major black eye for Mayor Bloomberg. Therefore, the only New York pro football team is in Buffalo and they would love to move to Toronto. The pro football situation in New York City is not entirely different from Los Angeles.
Yes, for a while, many City Councils were willing to spend taxpayer $$ to “put their town on the map”. Taxpayers are not longer happy with this, nor are the public tax purses so fat as in the past.
It’s true that most big cities are going to have other entertainment options, but I think the sports culture is different on the west coast. The weather is typically going to be nicer. People on the west coast are going to go to the beach, or other outdoor activities instead of going to, or watching, a sporting event than those on the east coast. In other places teams are part of the community going back generations. West coasters are typically from somewhere else, and keep their sports allegiances, or pass them on to their kids.
Another reason is that the NFL already went through a period with an odd number of teams, and doesn’t want to do it again. If LA gets an expansion team, then so does someone else - and there aren’t any really promising markets left in the US. San Antonio is the only plausible one, really, and it’s marginal at best. Toronto might be a possibility, but only by destroying the CFL (which the NFL does find useful), and the Bills might move there preemptively if it starts to look like a possibility.
So LA pretty much would have to get a current franchise to transfer. But with effective revenue sharing, there is not as much incentive for a team to move as with, say, baseball. Plus, there would be the difficulty of establishing a fan base in a sports market notable for its lack of capacity for true passion. The Raiders tried and failed at it already.
And in another state. 
In the same metro area. So what if there’s a state line passing through it?
I don’t think that’s it. The Bay Area has two football teams, two baseball teams, a hockey team and a basketball team. The L.A. area has two baseball teams, two hockey teams, and two basketball teams. San Diego has a football team. California does not, in general, lack pro sports teams.
Ed
So we’re back to the aforementioned “We don’t like football.”
Actually, that’s a bit of an over-statement, it’s just that we really don’t care one way or the other. We aren’t going to pay money to build a billionaire a stadium, and our passion and zeal are reserved for sports that really count, like baseball.
I think a big problem with building a football stadium is that it’s needed for fewer then ten games a year, making it difficult to amortize the costs. So how can it be used more often than that? Could it be used by a college football team as well? What about Major League Soccer? How does the LA Galaxy do? In Europe and South America, they fill stadiums for soccer matches and there are thousands of immigrants in LA, so you’d think it would be more popular than it apparently is.
Dude, do you know where San Francisco is?
Anyway, I grew up in the Bay Area and whenever people talked about why no one went to baseball games, this was the reason you heard a LOT - there’s so much else to do here! We’re so fucking cultured! Unlike in all of those boring flyover cities, you know. They have to go to BASEBALL GAMES because they don’t have…what do we have here, again, besides smugness and Starbucks?
Then the Giants built a new ballpark that wasn’t an icy shithole. And it was sold out straight for years.
My point is: I don’t think this is a valid reason.
Why doesn’t LA have a football team? Because they don’t want to spend lots of money on a new stadium or rebuilding an old one, and they got burned by their last two teams. Also, they’re just used to it now, probably.
I never said my theory didn’t have holes, or was rational. I admit that it is partly inspired by my disgust for TV executives that think it’s more important for people on the west coast to see the beginning of games, than for anyone else in the rest of the country to be able to see the entire game and have it end at a reasonable hour.
The amount of sports teams on the west coast, I think, is related to businessmen that think they’re going to go to California and make a ton of money. They are able to get decent attendance if the teams are competitive due to the big populations in California. (See the Giants and their sell outs when the stadium was brand new, they were winning, and had a record setting home run chase to sell tickets.)
As for hockey – and I know San Jose does well with attendance – I don’t think there should be any hockey teams anywhere that ice does not naturally occur.
California does OK in terms of attendance for most sports, but again, that is due to the amount of people there. Phoenix is not a very good sports city (not worthy of four professional teams at least).
As I said, I’m not saying this makes any sense, and relies heavily on my skewed personal biases.
Let’s get something straight: the NFL really, really wants a team in Los Angeles. It’s DEFINITELY in the best interests of the league as a whole to have a team in Los Angeles.
But it’s not necessarily in the interest of any particular team to move there.
I happen to AGREE with those who argue that sports franchises should build and maintain their own facilities. And I respect taxpayers who refuse to subsidize sports franchises by building them brand spanking new stadiums.
Problem is, so long as most OTHER big cities ARE willing to subsidize teams, there’s no good reason any team should go to Los Angeles.
There are many cities much smaller than L.A. that want desperately to be perceived as Big Time, and are willing to shower money on football franchises, because they think an NFL team is proof that they’ve arrived! Los Angeles, on the other hand, has nothing to prove to anybody. They ARE a big time city, and to Angelenos, an NFL team would nice, but not essential. There are loads of people in Pittsburgh who live and die with the Steelers. NOBODY in Los Angeles lived or died with the Rams. A football team would give Angelenos one more entertainment option, in a city that’s BURSTING with options.
If the Jaguars or Vikings said, “We’d like to come to Los Angeles,” the mayor would say, “Great- hope you like the Coliseum.” And that would be the end of that. The Coliseum wouldn’t generate the kinds of revenues that teams are dreaming of.
The Nets do not play in “The Big Apple.” The New Jersey Nets play in New Jersey.
And regarding the Giants and the Jets…what’s with all you people in other parts of the country claiming that parts of New Jersey are really part of New York. There was a recent thread where someone from somewhere in the Midwest kept insisting that Hoboken was in NYC. Or rather, he conceded that it was technically part of NJ, but for all intents and purposes, was part of NYC. 
Sorry guys, but while the Jets and the Giants are “New York” teams, they play in New Jersey. Most everybody around here is okay with that. You should be too.
There is talk of building on in San Jose or Santa Clara. It is ok with me as long as no public funds are provided. If the owners want one they can pay for it.
I agree with La