Because they don't pay well. And sometimes don't pay at all. Nobody is going to pay you for just knowing 1000 things that happened some hundreds of years back. Such knowledge is not useful to solving any pressing problems that exist currently.
You really should read your Marx. We're in an overproduction crisis: the world's most pressing problem is its lack of problems to solve.
You really should read your Marx. We're in an overproduction crisis: the world's most pressing problem is its lack of problems to solve.