"Engineers" need to constantly re-skill themselves as well to avoid being obsolesced every few years. Lawyers, doctors, and business managers don't, because laws and human biology and behavior don't change very much very fast. But there's not space in the economy for everybody to be a lawyer or a business manager. The Army only wants one officer for every 10 enlisted people, and one might suspect occupational class ratios are similar in the various civilian economic sectors.

(The ways and reasons the AMA keeps the supply of doctors artificially scarce is a whole other subject, suitable for hundreds of articles in itself.)

For better or worse, "vocational training" points The People to where The Jobs are. Studying great literature and political theory doesn't get anybody a ruling class job. Having pre-existing nepotistic connections in the ruling class gets you the kinds of ruling-class jobs you can get with an "educational" background in literature and political theory.