Cool magic items exist, we're agreed on that. So I, Lanefan the Fighter, go out into the field, clobber some bad guys, and come back to town with a cool magic item: a nice shiny....wand. I'm a Fighter. Wands make very poor weapons. I'm incapable of making it do anything else for me, so now what? Well, I happen to know this Magic-User who could make far better use of this wand than I ever will; and who is willing to buy it off me for cash. How is anything going to stop me from selling it, even if such is illegal in the game setting?