“The question is “what do you think about rabbis attending or not attending simchas”.
Personally, no different than how I would feel if my brother did or did not attend my Simcha, IF I was close to the Rav. If I was not, then it would “bother” me the same way it would bother me if 2nd cousin yankel didnt show up.
Then again, if I was close to my Rav, and he didnt show up at a Simcha, I would ask him if everything was ok just like i would if my own brother didnt show up at my simcha.