I'm assuming the OP is talking about additional tipping and not what is auto charged, when stating they didn't tip.
We've been on 10
DCL cruises. On all of them we left the 'auto' tip in place, so everyone received something. However, on 2 cruises we did not give the MDR servers any additional tip because we didn't use the MDR for those cruises so they received the auto tip for, I guess, services they provided on CC. Our first cruise we didn't leave any additional tip for the room attendant because in the 3 days we cruised it was a different person every day - sometimes twice a day - so we figured the person assigned to our cabin was sick. We found this confusing and didn't tip extra. One guy was in a white officer uni.
On two cruises we were all over the place with our schedule and a few times attendants missed our evening service but that was our fault. The service provided otherwise was wonderful so that additional tip was reflective on service that would've been provided if we'd've let them. One room attendant we tipped less extra because I constantly had to remake the bed along with having to put up with DH telling me to stop and call the attendant back. Apparently, some people don't mind sleeping on wrinkles but I'm not one of those. LOL
My last comment on tipping relates to the land portion of our vacations. We leave a tip even if staying for 1 night because we use everything - bathroom, kitchen, bed - we touch it all and the room definitely needs to be put back in order. So yes, IMO, a 1N stay needs a tip.
My comment on the Room Occupied tag is that when we hang that on the door we REALLY want to be UNDISTURBED. So all of those who hang that tag on the door all day are a PITA.