Because you live in a wealthy, white, educated neighborhood.
There, I just answered all of your questions.
I live in a middle to upper income city that is predominantly white. I’d say less than half of my friends had degrees by 23 (or even now, when we’re in our mid-20s). Most of their parents made it to middle to upper class by working at Ford on the assembly lines, No degree needed. (And my friends don’t have degrees because their parents couldn’t afford college and they themselves can’t find decently paying jobs.)