If this side of things ever hopes to build some institutions instead of expecting people throw their kids to the university system to be taught by their enemies, it's going to have to encourage people like Doc Brown to identify and apprentice bright kids.

While I'm on team "not everyone needs to go to college", it'd still be a shame to see genuine talent wasted on something far below their abilities because nothing exists to cultivate those talents.

But putting that all aside for the moment, everyone else in the town thinks Doc Brown's crazy, so perhaps he just likes being around the one person who doesn't (and perhaps even looks up to him), even if that one person is a teenage kid.