A juvenile detention center is a jail for children. “Juvenile detention center” is a euphemism for “child jail.”
Whether or not you think it’s a good idea to put children in jail, you can see that the people who named “juvenile detention centers” had some doubts about it. If the idea of jailed children didn’t make them uncomfortable, they could just as easily have called these facilities “child jails.”
Instead, they settled on “juvenile detention center,” which has three times as many syllables as “child jail” and draws your attention away from the children who are locked up inside.
There are some differences between child jail and adult jail. Children are allowed to go to school in child jail — adults have no such rights. But the basic idea is the same.
Why not call them child jails, then? Really: Why not?