"I can tell you we learned a heckuva lot about planetary evolution and lunar geology from those samples. "
That and velcro makes it all worthwhile.
That's the point. "Useful" to whom? If all you care about is money, you might as well go crawl away in a hole somewhere to die, pinching those pennies in enfeebled fingers. Real visionaries, the people who actually contribute to the advancement of humankind, know that learning, understanding, and wisdom all spring from the same source. Expecting immediate, monetary payoffs from efforts that, by their nature, have long-term, sometimes unforeseen, benefits, is the hallmark of a civilization in a state of decay and increasing decadence. Like I said, think small, be small.