People make life choices based on how things are, not how they ought to be.

Generally a “gold digger” refers to a young woman who marries an elderly rich man with the intent of gaining a large inheritance, not a young woman who marries an established (but still working) man a few decades her senior with the intent of raising a family. A big “gold digger tell” is that the rich guy already has adult children who end up in a feud with his new young wife (because she represents a threat to their inheritance).

Some men love gold diggers my uncle is one such man. In his own words "gold digger are the easiest lay".

It's fucked beyond measure

Maybe you need to flip the idea and date a rich 19y/o Instead

The question is “why would anyone want to date someone much younger than them (presumably up to a couple decades)?” not specifically about dating a 19 year old.

Not everyone can accrue a bunch of resources over time of course. But your odds of doing so are much better in your working years than when you’re in school.