Some adult kids stop calling or even visiting their parents because their parents were abusive to them as kids when they were living with them.
Just because someone is your parent is doesn't mean that you have to love that person even if it's your mom that gave birth to you.
It takes more than just popping out a baby to become a parent.
A good parent is one that cares for their children, loves their children and wanted to have their children because they want to have them and love them.
Some people have kids and don't really love them and can be verbally abusive or physically abusive.
They may have been molested by their parents too or used in other ways.
Or their parents could have done something later on in life that made them mad at each other and they no longer want to visit them.