Once a teacher admits that his lessons have little or no practical use, he usually retreats to the view that it doesn't matter what his students learn. The important thing is that students are "learning how to learn."
One thing I've been learning lately is that psychologists, under the heading of Transfer of Learning, have been empirically debunking this cliched rationalization for over a century. Here's a snappy quote from pioneer debunker Edward Thorndike:
Man has a veritable passion for keeping up habits merely because he has them; there are men who would rather beat a sick child than write "thru." In education man often excuses himself in these futile conservatisms by the hope that such cherished antique fads may have magic potencies on the mind as a whole.
Perhaps this is the first in a series of quotes from the Crusty Curmudgeons of Psychology...