Re: Epic win!
Funny you should mention the 'commoners do it' idea. I flirted with that a little, but nothing came of it (terrible pun not intended). The version of Kyouya in my head was just not finding the sexy in dirty, hot, cramped commoners' cars, so I went for this instead because I love the idea of them in tuxedos.
I actually haven't read that much in the fandom, though I've written a couple of things for it, so I wasn't sure how bottom-ish people usually wrote Tamaki. I tend to see these two as a switch-hit kind of relationship, so neither of them ends up too much towards one extreme or the other.