Because apart from 9 Volt and Jimmy T (and Penny Crygor, since her father is a main character in the series), pretty much no one seems to have any relatives.
Mona? No family seen.
Kat and Ana? No family seen.
18 Volt? No family.
Ashley? Her grandmother is mentioned, but her family is never seen or mostly mentioned.
Young Cricket/Master Mantis? No family.
And so on. I know it's common in fiction for story reasons:
http://tvtropes.org/pmwiki/pmwiki.php/Main/ParentalAbandonment
Or maybe:
http://tvtropes.org/pmwiki/pmwiki.php/Main/InvisibleParents
Are they all dead or something?
Mona? No family seen.
Kat and Ana? No family seen.
18 Volt? No family.
Ashley? Her grandmother is mentioned, but her family is never seen or mostly mentioned.
Young Cricket/Master Mantis? No family.
And so on. I know it's common in fiction for story reasons:
http://tvtropes.org/pmwiki/pmwiki.php/Main/ParentalAbandonment
Or maybe:
http://tvtropes.org/pmwiki/pmwiki.php/Main/InvisibleParents
Are they all dead or something?