HOW DARE YOU!!!! THIS IS THE INTARWEB!!! Of course my opinion is my opinion, but by default, when expressed here, it is far more important and correct than your paltry, pathetic reasoning skills!
Yes, teamwork is often a function of the players more than the system. My point, though, was that they system of 3.x rewards "lone wolf" highly individualist modes of character creation and play with no reward for teamwork (except a few minor bonuses) while AD&D and OD&D systems virtually enforced the teamwork aspect by making each PC reliant on his comrades for success.
It's a function of different mentalities and zeitgeists. Back when D&D was first loosed upon an unsuspecting world, people were, simply put, more social, more group oriented. Now, people are far more individual, less concerned with the group as they are with themselves. They don't call it "the Me Generation" for nothing you know.