Tritely answering the title: Because the process of evolution has selected for organisms that are highly motivated towards reproducing. Organisms that aren’t highly motivated towards reproducing have been out-competed. The process of evolution doesn’t really care about how good of a parent you are, as long as your children also reproduce.
More directly answering the question: It helps to invoke the Principle of Charity, and assume that people are well-intentioned, but perhaps unskilled at parenting. Regardless, realize that life as a minor is only a fraction of your lifespan, and that having suffered under bad parenting sets you up to realize what not to do with your children.
Tritely answering the title: Because the process of evolution has selected for organisms that are highly motivated towards reproducing. Organisms that aren’t highly motivated towards reproducing have been out-competed. The process of evolution doesn’t really care about how good of a parent you are, as long as your children also reproduce.
More directly answering the question: It helps to invoke the Principle of Charity, and assume that people are well-intentioned, but perhaps unskilled at parenting. Regardless, realize that life as a minor is only a fraction of your lifespan, and that having suffered under bad parenting sets you up to realize what not to do with your children.