Lets harm all the kids who actually know what they want to do, have construction, IT and hospital work done by uninterested stoners (because what else are young people going to do when they have no options)?
Would it really be a much higher percentage than the work done by uninterested stoners now? Lots of people already have jobs they aren't particularly excited about and just fell into. At least this way they'd get a chance to try out a few different things first.