As a practical matter, philosophy is typically studied by those who will go on to law school, a Masters in something employable, or as part of a minor or "core curriculum" alongside a trade.

In most of the liberal arts and humanities - particularly philosophy, a graduate from a reputable institution will have extremely sharp critical thinking and writing skills. A philosophy major's daily grind is very similar to proof-based math. Across the disciplines, people are mostly writing papers that argue positions. Particularly at top-tier institutions, those papers are held to a high standard for quality of argument, evidence, and style. It may not correspond directly to an efficient way to turn capital into more capital, but it's hardly a "waste."