Because it doesn’t seem to matter currently if you play ranked games or casual games, the general experience tends to be the same. But one has numbers and things to go with it. You still get people playing to win in casual games and you get people dicking around having fun in ranked games, and the ranks don’t necessarily indicate how they play as a team and a whole bunch of other things that make it less than ideal.
Well I can tell you never actually played in that era, because it did happen. Just on the SLAUGHTERHOUSE TF2 servers, in which I myself was an admin, would kick players who completely dominated a game over to another server where they would fit in better. This was a pretty common practice. Not to mention the admins who power tripped and would kick anyone who killed them too often or claim everyone better than they were was cheating.