How do I kindly tell my stepmother to stop buying me random crap for Christmas every year?

Every year my stepmother buys my sisters and me really crappy, cheap, random gifts, usually things you'd get for an 80 year-old. (We're in our 30's.) Two years ago I received a shapeless, fuzzy yellow nightgown with pink flowers all over it, that zipped up the neck. The year before that I got a black felt hat from JCPenney with leopard print side flaps that you tied under your chin. We've received hideous bathrobes and cheap travel mugs. I just got word from my sister that it's another old-lady nightgown year. My sisters and I are particular about our styles, but we are not selfish. I would much rather my stepmother make a charitable donation or take us out to dinner. It is a waste of her money to buy us this stuff, just so she has something to wrap! She obviously doesn't put thought into it, since we get the same things over and over. How do I tactfully tell her to stop giving us this stuff? I don't want to come off as unappreciative, but it's getting ridiculous.