Because it almost entirely replaced traditional server browsers, and it usually sucks.

Traditional servers were awesome since they encouraged developing a sense of community with other players, there was a more social aspect to it, you only had to wait for the map to load and there was no weird five hour lobby pause.

And for a game where it is 1v1 it might not be that bad. Imagine trying to slot 10-128 players into evenly distributed teams. One side almost always ends up stacked.