Another perspective on it is (one I think Americans are specifically averse to) is that these are all simply correlated to "class," for some definition for class. This is really another way of saying people follow in their parents footsteps.
If you are born into a reference group (parents, uncles, etc.) where most people have children in their early 20s, you are more likely to as well^. It's expected and seems normal. If you are born into reference group where educational achievement, college attendance, profession etc are within some band then you are more likely to find yourself in that band too.
If your reference group is a family and friends circle where college is a rarity, then attending college becomes overachieving. Most people are no overachievers. For others anything less than a top college, higher degree, top-of-your class is underachievement. People do what they feel is expected of them.
This is one of those things that people take for granted in individual cases (like their kids) but not at group levels. IE if you and your wife are highly educated, you expect that your kid will go to college. You don't think his chances are represented by national averages adjusted for income, race and intelligence.
^The parenthood point is a bit of a strange one because cultural shifts have been at work over the last few generations.