Sophiegirl,
I suspect the downgrade to paper coffee cups in more to try to save money related to processing the mugs (washing, breakage, replacing with a clean one each day) than hygiene. They still have two sets of glasses in the room and use mugs in the concierge lounge. I'd rather Marriott reevaluate this new downgrade rather than give me a mug that I'll just probably leave at the hotel rather than take it home.