The thing about parenting that a not insignificant proportion of parents would rather ignore is that it isn’t just a job you do on the good days. In fact, when somebody is a mom or dad it is even more important to ride out the bad times and try to find solutions to them if possible. In most cases, parents are the primary support system for their kids as they grow up, and if they don’t step up to that responsibility, the situation can deteriorate rapidly.
Another downside to this negligent parenting style is that it doesn’t just fail the child, but often the people around them, too. It isn’t pleasant to be a family member to a kid who is acting out. When this starts to put strain on a family, it is more than some childhood rebelliousness that is going to become a problem. Every relationship will suffer.