I find Hero fun. Which is weird because they're opposite to Hayato in so many ways - stronger, slower, less mobile, less skills to use - yet I enjoy it a lot. I guess I would choose them because it would be a nice break from all that flying around I do, and it would give me a chance to experience Maple through a different playstyle.
I feel like people would or should pick one with a different play style. My main is paladin and as much as I love having the most ideal dps on most bosses (don't have to move to dodge attacks when you block %hp attacks and have auto potion heal on pets) I dislike the single style attack sometimes.
I play zero on the side because I get to go fly around on alpha and smash things on beta. It's a huge contrast to single a single button tank and attack style.
Main is a NL, but I'd play my Mihile more without it.
Edit: As to why, I just enjoy the playstyle. I know most others don't really like it because Royal Guard makes the job more difficult to master than others, and without it, the job is just meh. But I liked putting time into practicing it and it's so rewarding as a result when I'm constantly smashing enemies with it! ^^