This does not work with teenagers, in whom bedtimes are practically unenforceable, but whose need to get to school in a timely fashion does a reasonable job of imposing a getting-up time. They are chronically sleep deprived. Smaller children, I imagine, have even less of a chance of managing the feat.

It seems like it's a near/far problem, at least in part - it'd take a few weeks, perhaps even a month or two, for the kids to figure it out, and in the meantime the parents will be inconvenienced by having to deal with cranky kids, and also probably having to stay up later than they'd prefer to. I suspect most parents don't give it enough thought to realize that the situation would be temporary (well, not counting the possibility that the kids could settle into an inconveniently late bedtime) and the lesson would be valuable, though, or they don't believe that their kids would figure it out at all.