And we always remind guests of this when they ask if it's okay to bring their bags to the bus with them...we tell them that while Disney says tipping is taken care of when using DME, it is ONLY for the tips for luggage delivery at the resort, not for the bus ride.
There is signage that states gratuities are accepted. I don't need someone verbalizing it to me...seems way too much like begging. I try to sit up front on the bus. That way, when I get off, those behind me will notice (hopefully anyway) me tipping the driver as I pass by. I have seen families get their 10 bags, unstowed by the driver, and walk away,,,no tipping. Now, that bothered me. That driver should have been tipped..he delivered a service besides driving that bus.