Why some parents are deadbeats

I think some parents are dead beats because something happened in their life and they didn't fully recover over it but they don't know what to do. Also Some people have made major mistakes and don't know how to deal with their mistakes or have different ways to deal with it.

I  really don't think there is a true def. for a good parent. Each parent has a different def. for a good parent you could have a good mom but someone Else's mom could think she's a bit harsh or to easy on you. There is really no def. of a good parent. But a good parent doesn't kill there kid or treat completely horrible, is obviously not  a good parent