Because you couldn't prove ownership of the several hundred thousand dollar piece of art, which is the real point of this whole thing, conspicuous consumption, because when poor people have found a way to make fakes of all your clothes and wear them, and influencers can post pics of their rented Lambourghinis that look like the ones you take with your you bought with cash, having a public digital wallet that proves your unique ownership of an expensive item is the new way to show off status in a way that can't be duplicated.