Trying not to reject things that aren't familiar to me...
Maybe this is like the opposite of baby-sitting. Like child-less parents who want children but don't want them all the time could rent children and like act like they're their own. Or it could be like temporary adoption, you know, like the real parents don't have anyone to watch their kids and ... yeah.
Or we could look at it like some form of those dating websites except it's for younger kids and the parents know what's going on. Since client feedback shows they've been renting girls to make it look like their sons aren't date-less.
Still, the last use is kinda sad... what would you be teaching your son if you rent a girl to go out with him -_- that if you don't have friends you could just buy them?