I think it's our attention span.
Look at the products in a convenience store or the grocery store. There's gotta be 32 types of one thing or it just isn't right. There's a hundred different kind of Oreos and M&M's, just in case someone gets bored for one second and forgets to spend money.
We won't even sit through a movie unless there are 3 sets of boobs, a couple good explosions, and a few severed heads rolling around within the first 15 minutes.
If you took 99% of classic movies, like The Shining or One Flew Over The Cuckoos Nest (off the top of my head), put one on a screen in front of a room full of viewers, the theatre would be empty in half an hour. No time for a plot to build, ya know?
I'm not finger pointing, I'm as bad as the next guy.
The only reason I've ever given it much thought is because all the "choices" stress me out. I don't want it my way. I just want to "eat it or starve" like the old man said.
There's comfort in that.