Quote Originally Posted by Erik Setzer View Post
It's like a weird trend of killing the adults outright or just having them leave.
It's incredibly common in fantasy / adventure stories because if a person has a family they have people to care about which, as we see with Luke, only serves to tie them down. Kill off the parental figures and suddenly they're free to go off on a damn fool crusade without having to listen to anyone any more.

And as a bonus they might even get some angsty mourning out of it (if they're male - women like Leia get to comfort heroes like Luke over the death of a guy he met like two days ago rather than have her be bothered with all that torture she went through before watching her family, friends and entire planet obliterated).