If you don't order room service or use the bell staff no need for comments [inapt text edited by Moderator].

If you do order room service, do you tip the delivery person? If you use the bell staff to carry your luggage do you tip for that?

If yes to either or both, do you also tip the housekeeper each morning since all three jobs are identical in that the person is getting paid by the
hotel, yet doing a very personalized service directly for you so naturally if you tip any of the three you should tip all of the three.

For those who tip the room service person and/or the bell staff but don't tip their housekeeper, I suppose Marriott is correct in that non tipping of housekeepers is due to the lack of direct visual connection with the person doing such a deeply personal task directly for you.