For gay men, sex is not utilitarian. We do not use sex as a means of reproduction, as a way to establish a socioeconomic dynasty, as a means of gaining status in the world at large. Our desire is our own, what sets us apart, plain and never simple. Which is not to say that every gay man thinks it's a great idea to explore the more baroque perversions. Vanilla can taste good too.
Heterosexuality suffers from millennia of enforced, standardized power dynamics.
When it's just guys everything is up for grabs. Also, the male of the species is just plain expected to engage in power plays, both in the sack and in the world at large. Putting on leather just makes it all more visible. One might argue that the playroom door is a kind of magical gateway, and when we enter a dungeon space, we leave our civilian selves behind. The deeper we go into the dynamics of consensual power sex, the more we dance along the knife-edge of ambiguity.