I dont think we used our Scenic butler - he did come in when we arrived and explained how everything worked and how to contact him -
DH once had his dinner in our room via room service, not sure if the butler brought it/ organised it or who did (I went to dining room as usual)
We did not contact the butler for anything else. I'm sure he would of given excelllent service - we just didnt really want any service.
"Butler service" sounds fancy - but, for us, we enjoyed our cruise perfectly well without ever using or wanting to use one (that I know of, perhaps there are things a butler does that you do not notice - but not sure what they would be?)