I find HU is more of a who blinks first game than a test of actual poker skill. With that said plenty of the biggest bankrolls in the world come from HU games.
It's an oversaturated market for sure. Players often have a few go to sites already. Hard to convince players to try something new when they have reliable options.
I use my winnings to buy into bigger games once my roll allows. Just progress buyin levels until I'm playing the best games available. With That said the biggest tournaments I've played regularly were $50 sit n go's back on Full Tilt.