1. It is comfortable and all buttons are very easy to reach quickly.

2. In tournaments there can be hundreds of entrants. All available controllers up to this point were connected wirelessly one way or another which means that something new had to be invented to prevent interferences. This hub was the answer, and making it support Gamecube controllers is the only way that makes sense since people who show up at tournaments (a.k.a. the target audience) tends to prefer Gamecube controllers.

I never thought of that, but it makes total sense.