Additionally, most (actually) emotionally well adjusted partners want no part of that kind of deal (at face value) for very real and legitimate reasons, so the partners that do end up matching up will often be those who are either lying to themselves (neglect) or others (abuse) about their own emotional state or their own plans.
And boom, we have the wheel and the multigenerational cycle of abuse.
You are never taught how to properly tend to the emotions of both yourself and others, so unless you pair with an emotionally well-adjusted partner, you will lack the emotional knowledge required to teach your children better. And what's worse, your brain will relapse into the habits it does have experience, which may often be negative.