Well, we do for a lot of things. But sometimes I might copy an article or something for a paper for a class, or something as such. I can cite it however I want, but I'm still using copyrighted material for my class that I don't have permission to use (well, sometimes; some materials give a specific okay for educational purposes). But even then, that doesn't really change the argument nor the result: yes, they could stop me if they wanted to. It's within their right! They don't because my usage is so small that it barely matters. It's just not the same scale.
It's like comparing a massive torrent site versus a guy photocopying sections of a rulebook so that everyone in his group can have access to that section without owning a book. One is closer to an actual problem, the other is not.