It's simply acknowledging my status as a human being.
I'll submit that some aspect of keeping kids in school is an attempt to keep those kids out of small trouble now and big trouble later. Paternalistic laws/rules very often rub the most responsible members of society the wrong way when they apply them to themselves. Moreover, applying rules for children to adults will also push your intuitions in a certain way.
Believing in a kid's potential to be a productive member of society, I'd argue, is an even more edifying way of acknowledging their status as a human being. Your version when applied to poor city kids is basically, "sure, it's cool if you want to go become a vandal/drug dealer/future inmate; whatever."
Also, you're giving kids too much credit. Kids will almost always maximize short term payoff at the expense of long term success (hyperbolic discounting?). And good parenting is about balancing those inclinations. In the absence of good parenting, schools can pick up some of the slack.