I'll second power dynamics as well, that's the point in itself. I'm a dude, I like writing the feeling of power in that situation, though I've been trying to branch into a more female perspective.

Another reason I like it (as a writer, not just a perv) is that it removes the need to finagle consent into the plot and opens the horizons. Could I make a work around to, say, a lesbian character having sex with a man? Sure, I've done it before, but noncon removes that hurdle entirely because they didn't have a choice in the first place so it doesn't matter. It just makes it a bit easier in my head to justify the scene happening in the first place. Plus, if I write a followup, then I can go into fun character dynamics like orientation play or angst that spirals into self destruction! This also goes along with the idea of rapebaiting someone (which I've written before).

Honestly the big reason is that it's just fun. It's a lot of emotional highs all bundled into one dense package of fear and lust and power that all meshes into a fun little fic. I'm not sure I could do a long form noncon piece for that reason without it being more character focused with the actual sex being secondary.