Because doing what they want is doing what they want, nor what you want. That in its very essence is fun. Right now QP is the only place you can actually use a whole bunch of the heroes, particularly snipers, because they're just not viable for comp. The kinds of people I might be actually pissing off in QP by doing so aren't the kind of people I mind pissing off, frankly. I doubt if I am pissing off 5 people anyway, most people can handle the occasional loss.