My guess is, that they give some sort of credit for it, i.e. you earn an academic credit by doing it which would be consistent with the "dumbing down" of the educational system.
It's easier than teaching.
I'll second your sentiment and add that "mandatory" community service is being used to enforce the Communist belief that we have a "duty" to serve our fellow man. Never mind the Constitutional ideas of personal responsibility and initative. These programs are being utilized to groom our children for citizenship in a collectivist/socialist, one-world order society. These programs are also direct decendents from UNESCOs "Rights fo the Child" progroms....