>>40166626 (OP)Because you get to make a bottom squirm and move around in pleasure using only your dick.
And you get to pin them down and manhandle them. So its kinda like the rush of bullying someone AND having sex at the same time.
Like remember when you where a kid and it was snow day and all kids had a snowball fight, someone pissed you of a bit and you just grabbed them and showed snow right in their face? Its a rush like that, only you don't feel bad afterward because they love it... and instead of snow you use cum