I know that widescreen versions of movies show more of the total picture, but what would be missing from a TV broadcast? Is it for widescreen tvs?
If you’re refering to a show like The West Wing or Enterprise, its often because a widescreen image is seen by many eyes as more artistic and professional. If you also factor in things like the superbowl, then yes they are certainly doing it to appease widescreen tv owners. Why? Because widesreen tvs cost more, so people who own them are the kind of viewers advertisers want. If the networks can boost the average disposable income of their viewing audience by broadcasting in widescreen, then they’ll do it as much as possible.
So, people that buy really expensive TVs expect to see slighly less material than people with regular TVs? There has to be some sort of ratio argument here, otherwise, isn’t it just a pointless sizing issue?
This site from the UK explains how tv is moving towards a widescreen future and explains the differences between formats in pictures much better than i ever could in words alone.
mcbiggins apparently misunderstood the OP, which is: When a television show is shot in widescreen, what do you miss when you watch that show on a standard 1.33:1 television screen?
The answer is: You don’t miss anything. The widescreen version of a television show is broadcast on a different channel than the letterboxed version. For the version seen on a standard television screen, the image is letterboxed, i.e., the image is shrunk so that you see the entire image on your 1.33:1 screen, and black bars are inserted above and below the image to fill in the blank areas created by the shrinking.
However, sometimes networks prefer not to use letterboxing for television shows that were shot in widescreen. In that case, a person watching on a standard 1.33:1 television screen will be missing some of the left and right sides of the frame. But the director and cameraman are usually aware of the network’s preference, and when filming scenes they will keep the most important characters and action within a central 1.33:1 area of the widescreen frame.
No, mcbiggens is right. Shows like ER and Angel are shown in widescreen for the cinematic appearance that widescreen gives television content.
You’re misunderstanding the OP too.
Shows like ER and the Super Bowl are being produced in HDTV now. The standard aspect ratio for HD is 16:9. So, to show an HD program on an old-style 3:4 screen, it will be letterboxed.
Embrace the future. Not very far from now, manufacturers will eventually stop producing 3:4 screens. Expect this to happen once digital / HDTV finally becomes the US standard. It’s been delayed time and time again, but it will happen eventually.
Perhaps, but you don’t have it quite right either. Shows like “Everybody Loves Ramond” and “According to Jim”, among others, are also shot in High Definition/Widescreen format, but aren’t broadcast in letterbox on the non-digital stations.
I’m assuming that they cut the sides off for the regular broadcast.
-lv
Maybe you should re-read what I wrote, as I already discussed that: “However, sometimes networks prefer not to use letterboxing for television shows that were shot in widescreen. In that case, a person watching on a standard 1.33:1 television screen will be missing some of the left and right sides of the frame.”
Girls, girls, you’re both pretty. 
Really, you’re both right, for what you’re talking about. Directly addressing the OP, it’s true that nothing is “missing” from the picture to necessitate the widescreen broadcast. In this respect, widescreen TV isn’t shown that way for the same reason a widescreen movie is.
So why does it happen? Well, it’s also true that the reason this is being done is the future, when widescreen HDTVs are assumed to become the new standard at some vague point from five to eight hundred years from now. The real money in television is not in the original broadcast, but in syndication, when the already-produced show is sold into reruns.
Therefore, shows being produced now have to take into account future profitability for the next fifteen or twenty years, or longer, and thus many producers are adjusting their formats accordingly. If they stuck with the standard 4:3 look of ordinary TV, future broadcasts would either be squashed to fit the wider screen, or they’d be shown with black bars at left and right. Those shows would have an “old” badge, sort of the way the credits for “Brady Bunch” used to say In Color!, which looks kind of funny now.
And as has also been said, some shows are being produced with an HDTV standard but are being broadcast (for the time being) in “full screen” on the main network, with the widescreen version being shown only on the parallel digital channel (or going into the vault for however long it takes for HDTV to become the common standard), while other shows are being broadcast in widescreen because it makes them look more, I don’t know, grown up or something, and because the increasing popularity of DVD means people are used to looking at it.
Can we all get along now?