I've met loads of single parents who do an ace job, am I a single mum and so are some of my friends, but the fact is, statistically, more criminals come from single parent families than from 2 parent homes.
I'm not saying for a second that single parents are shoddy parents, but they are more likely to have less time for their children than a 2 parent family, they are more likely to have to work longer hours and have no one home to supervise from a younger age than 2 parent families.
Without support, even the most awesome parent in the world would struggle to hold down a full time job, working shifts and do all of the parenting all of the time, without leaving the child unattended for longer than they'd like, during which time the child is more likely to be getting into trouble.
This isn't the parents fault. It's society's. We are too quick to judge these days and less likely to help.
The only ones of my friendship group who went off the rails in their late teens/early twenties were the ones with strict curfews, draconian punishments and parents they were afraid of.