Even though L4D was originally designed as a PC game, I think they took to heart FAR too many principles of console gaming.
The way it turned out in the end, I look at Left 4 Dead as a console game that just happened to be popular on the PC. Just look at matchmaking, player limits, and even the controls scream 'console game'.
PC users are just not as inclined to bend over and take full priced yearly content releases posing as new games up the cornhole as console users are.
If it would have been a console-only release, I don't think anywhere near as many people would be complaining about the way they're handling the franchise.