In the ‘olden days’, the CSD did not have direct service responsibility so was freer to ‘float’ between cabins. These days, the CSD is the senior crewmember in Club World and is written into the cabin service. As such, the CSD has less time to do other things. If everything is going well, the CSD might visit all F passengers, but if another aircraft issue needs resolving (ie a problem in CW or Traveller) then they have to resolve that + still help manage the service in Club. So I guess it is a choice between leaving Club one person down or ditch the ‘non-critical’ tasks. Then again, on MF, the CSM is often stretched even more thinly as at least on Worldwide routes there are still Customer Service Leaders (formerly Pursers) in F and WT (they also used to have 1 or on the 747, 2 - one main deck, one upper deck -Pursers in CW - that role is now filled by the CSD).
I do find that senior crew set the tone for the rest of the crew. Anecdotal but if I have a CSD who seems indifferent (I’ve had a few but they are the exception) everyone takes their lead from them.