Earlier quoted context omitted.
The failure to obtain a college education has an external impact on the families, friends, employers, and coworkers of those failing to be college graduates. Failure to be a college graduate affects the ability to abide by social norms imposed upon everyone. In a developed nation with a safety net, failure to be a college graduate might even implicate society's need to rescue those who can't work or injure themselves…
We require people to get a high school education for precisely the reasons you state.
Just want to point out that here in the US we don't require anyone to graduate high school. In most cases minors are required to attend school. My point is that, in the past, minors weren't able to chose for themselves. Instead the guardian often chose to make the child work thus continuing a cycle of poverty.