Why should MIL like or approve of her DIL?

Re: Why should MIL like or approve of her DIL?

In a lot of cases the families have told their children the parameters of finding their own mate, yet the kids make their decision about their life-partner regardless of family opposition. And in those same cases the girlfriend or boyfriend knows that the other family will object to them - but there’s this belief that love will conquer all, including family resistance.