For the same reason some people love pre-op trans in real life, the feminine form with a touch of the taboo. Like what you like, it's a big world with room for all of the (consensual) kinks.
I draw a line between real Futa (Hermaphrodite) and Trans. One is a fully functioning girl that was also born with a dick. The possibility of self-impregnation is very hot to me but is hardly ever realized. Whereas the other is just a boy pretending to be a girl and I don't want to see it.
Straight Shota is great, especially paired with Loli; paring Shota with a guy turns me off, unless they are teaming up with a female.
Pretty simple, I like pretty girls, and also boobs. I also like watching girls get fucked, usually by penises. If the penis is attached to someone with boobs, such as a pretty girl, that's just a bonus to me.
Futas are kind of unnatural, which makes it more perverse, and can thus be a turn-on.
For shota, I really mostly like games where I am the shota, as I know what such a body could feel (I have been one, and of course I explored all holes and protrusions). I don't like most straight shota media, as any female that seems "motherly" in a sexual situation disgusts me for some reason, it just feels wrong.