Those of us with parents that raised as well should be thankful for having parents that were normal. Like living in poverty, having poor parents can play a drastic role in how you turn out when you grow up. Children need guidance and spaces where they feel safe. When a parent is a terrible parent and/or abusive, you take away both proper guidance and safety.
A situation where a parent is missing can also result in not so good upbringing. There are many factors that contribute to this, but statistically, children raised by single parents fare worse on average than one raised in a proper 2 parent household.