Why would a course in marketing help your career in some field other than marketing?

Marketing is the art of selling people things they mostly don't need, and invaluable human insight can be gained from this. While a course in marketing may be at some remove from this principle, there are surely similar lessons to be gained, and you will, after all, be more prepared to actually do a stint in marketing if and when that is in the cards. The typical upwardly mobile business resume will demonstrate at least some marketing successes.