A player is allowed to “give himself up”. There was a big controversy in Victor Cruz’ rookie season where he forgot it wasn’t college, caught the ball, went down, then left the ball purposely on the ground. Everyone, including this diehard GIANTS fan, was thinking “Idiot, that’s a fumble”, but the refs blew it dead and a lot of complaining followed. I liked that the call went my way, but IMNSHO it was the wrong call.
If the carrier were allowed to advance after touching the ground, I suppose every play would end with what is now a late hit penalty. Ball carrier hits ground, followed by several defenders plowing into him to make sure he is totally down.
The only winners in that scenario are the neurologists who get paid for treating so many more concussions.
Yeah, really. It’s pretty easy to see why you want the play to end. If the ball carrier could keep running, the defense would have to practically murder an offensive player on every play.
And that’s a problem how? 
As I mentioned earlier, that’s what actually did happen in the past and why tackling takes the form it does now. Too many broken/dead bodies.
How???
In American Football, the biggest commodity is tackling whoever is carrying the ball.
No, it was objectively the correct call, though it might feel wrong since it was unusual looking. If a ballcarrier gives himself up by intentionally going to the ground and ceasing his forward progress, the play is over. That’s what Cruz did.
…stop thinking rugby union and start thinking rugby league.
I didn’t see the Cruz play, but once or twice a season, a player (usually a rookie) will go down, - not by contact - and leave a live ball on the field. I remember Tedy Bruschi picking up such a ball for a touchdown after a rookie made a catch, tripped over his own feet and hit the deck. He put the ball down and ran toward the huddle, Bruschi picked up the ball and ran it in for six points.
Precisely what I was thinking, being from the South of England I only played rugby league a couple of times, but the parallel is obvious (even if in league the time to re-start play after a tackle is much less).
So one form of rugby is more like American football than another?
Lol and yes, its an odd game in that respect. However the ball can be carried forward or kicked forward which ultimately achieves the same result.
Ok thanks, makes sense.
However in both rugby union and rugby league players tackle each other hard (within rules against dangerous tackles) and keep on playing. Yes there are injuries but not many because the players are very fit. Soccer is rather brutal at a high level too.
They’re just pretending. 
Put a rugby player on an American football field and being “very fit” wouldn’t save him from serious injuries from illegal tackles.
…no they don’t “keep on playing” in league. When a player is tackled and held, play stops. It restarts once the player has rolled the ball backwards under his feet. If we were to implement what you suggest into league, then league would simply become another game of rugby union. And if you implement it into the NFL, then it becomes another game all together. The simple answer to your question is “because they like the game as it is, and don’t want to play your version of the game.”
Mike Pereira and Eli Manning disagree with you. The head of referees at that time agrees with you. I bleed GIANT blue (once the Yankees are eliminated or win the World Series; before that I bleed pinstripes), and like I said, I believe they caught a huge break on that call.
This is an uninformative and misleading answer and is unworthy of the SDMB. Rules of a game are set by someone often for a conscious reason and they change over time often for a conscious reason.
If answers like this were accepted, then we would never cure ignorance and we would never learn anything here.
…whatever dude. It is the correct answer and it isn’t misleading. And the same answer has been expressed by several other people in this thread but you didn’t blow a gasket over their responses.
It’s a crappy answer and it offers zero information. You could answer almost any question this way.
History? Science? Culture? Law? Religion? Why not answer every question with “It is because it is.” Why ask questions then?
And it’s also not true. The rules of football were chosen or changed for specific reasons, some of which have actually been expressed in this thread.
So what? Yours was the one that got my attention.
…we know why this question was asked.
“I like American football and in my humble opinion running further with the ball would enhance the game.”
We’ve had plenty of threads in similar veins. “Why don’t the make soccer goal posts wider? It would enhance the game!” Well to most people no it wouldn’t. The game is what the game is.
Well that was pretty freaking obvious, considering your over-reaction to my post.