I think the fear is the mixture. So you take impressionable youth and force them under legal obligation to spend more time with elders of their socioeconomic group who selected a life of crime often than time spent with their own parents. What could possibly go wrong? Optimistically they'll be scared straight, but ...
It's not like they're sending people sentenced to 40 years hard labor for robbing a bank to community service at the recycling center. They're probably mixing with people who got first-offense drunk driving or disturbing the peace charges.
