re: "It's useless because most people can't hear the difference."
Sure, but when sampling and then processing things, you can consider it "headroom". Just like it's not hard to edit a photo in a few steps that the limitations of 8 bits per pixel begin to show. Though I suspect sampling frequency is a lot more important there, 24bit can't possibly be "too much".
Yes, I understand that this is not a good argument for consumer products to be more expensive and need more storage, just so musicians of the future, or pirate musicians of today, can have a better time. So I think the best plan is to encourage everybody to become hobby musicians, then it would be an easy sell.