Sure his parents were childish and wacky!
But... They DID seem to love and care about Timmy deep down. If anything, they would at least love Timmy enough to not make him suffer in the hands of an abusive babysitter.
They don't listen to anything he says. They never did. That's what made them terrible parents.
shareHe really didn't need to. Thanks to wanda & Cosmo he could always get even with Vicky almost at will. There was probably also the "enemy you know" factor. Vicky never figured about the Odd Parents. If he got another babysitter, they may have started to notice things and ask questions.