Why are there so Many Orphan Heroes and Superheroes?

Because since a lot of Superheroes parents have often injusticely died in the hands of criminals (Batman and Superman for example), it has often prompted them to fight against criminals. A lot of superheroes decide to fight criminals and crime because they lost something from it (Punisher and Spiderman for example) and its their way to either "redeem" themselves by preventing others from experiencing it or just revenge.