Part of the rationale is, they need a much longer period of education if they're going to get a job, and there aren't any unskilled jobs available. Also nobody gets married until they're 28 or so nowadays, and unmarried young men tend to get into trouble and need a lot of looking after. This is just a response to the extended adolescence that we're seeing all over the modern world which is keeping young men in a state of dependency until age 30 or so. If they were apprenticed or indentured to older men, to whom they were not related (relatives might be inclined to be too lenient) and who were authorized to use frequent, moderate and reasonable spankings to discipline them, it would be a lot of fun, and and most of them probably deserve it.
Girls get out of school at 18-they mature earlier, and can marry older men. Incidentally, married men under 40 are required by law and custom to submit to reasonable corporal correction from their (usually younger) wives--reasonable means on the buttocks and upper thighs, no cuts, & no bruises lasting more than 48 hours--large wooden hairbrushes and humourously inscribed paddles are popular wedding shower gifts!. None of this is shown in the novel, however, which only has one briefly appearing, non-speaking female character.
All this has pretty much eliminated street crime but, sadly, has resulted in a lot of red butts, yelps, squirming and the occasional tear. Unfortunately, white collar crime has been largely unaffected, although there are few things that invite a good spanking more than a stylish young man in a well-fitting business suit. I'll have to make that the subject of a picture some day.