Have to wonder tho...what is wrong with just taking turns? Always seme or uke! If it really is love should they not be able to switch once in awhile? I understand that there r some natural born ukes/semes...but they ALL can't be like that, like how i read in most yaoi.
I'd probably switch maybe once in a thousand times. I currently don't have a penis, which means no switching for me at all. So if I get a penis, I will not let the topping option go to waste. I see your point though. But I'm thinking from the perspective of someone who doesn't even have an option currently.
Hmmm...maybe being a seke is not so bad too

If I had to reincarnate into a man I'll definitely be a seme, I mean, who wouldn't want to?(๑•ㅂ•)و✧