+1. It's really a joke for United. They give away an item that has no real value. Person ends up with a $15K tax bill on it and United gets a $35K write off. United ends up making money on the deal.
You forget to mention that the exploitable hacks (which must have been big to be awarded the maximum 1 million miles) are now closed.
People tend to be such suckers for large amounts without regard to the actual notional value.