My opinion only- For the middle class going to college is not seen as optional. Doing the same expensive activities as the other middle class kids is not seen as optional. There are millions of working class people in the US with good lives, but most middle class people would never seriously consider not following middle class norms.
So raising a kid who's middle or upper class is actually quite expensive, and that's part of why low income and high income families have more kids than middle income families. https://qz.com/1125805/the-reason-the-richest-women-in-the-u...