The purpose of a PhD is not to train people for "appropriate jobs". PhD students perform a large part of academic research, and while most of it is grunt work and produces incremental results, some brilliant people end up discovering a gold nugget and carrying their field forward many times over.

Innovation is hard, most ideas do not pan out, and most people aren't made for it. It really is a number's game: to stay competitive and innovative as a country you need enough people pushing against the frontier, including taking bets that are too risky for the private sector.