Doesn't ESPN or NFL Network show condensed versions of games? I thought they showed games just like Calvin like, shrinking the whole thing down to an hour or so.
In any event, there are tons of good reasons to watch the whole shebang. Unlike baseball, there's a ton happening on every play. Seeing a replay with somebody knowledgeable pointing out things you might have missed is fascinating. Plenty of times a crucial block or a pick will happen off camera, or a receiver that didn't get thrown to will have been exceptionally well covered. Second guessing is also a big part of it. [Most] Coaches aren't infallible.
The most important thing is that a good game needs that pacing. Particularly once you get into the playoffs, which have been unbelievably good the last few years, you need the drama from the first 3 1/2 quarters to really setup the ending.
Now, let's all go and talk about deflated balls in Josh's NFL thread.