Two possible reasons are a) that there are a lot more celebrities around than there used to be.
There was a music programme "Which is the best decade to listen to music" and the answer put forward was NOW. As we can now listen to music from the 50's, 60's 70's 80's etc etc
In the 80's you could not listen to music fomr the 90's or 00's as it had not been made yet.
Similarly we have people who became famous in the 50's onwards (and older) still alive, plus new people becoming well known at the moment.
Another factor b) might be "delayed substance abuse" effects.
Not pointing any fingers or criticising anyone, but it is a fact that a lot of artists died in the 60's and 70's and 80's from recreational drug overdoses.
Those of their contemporaries who survived that era, but did have large habits for these types of drugs, could now have undiagnosed conditions as a result, like weakened heart,, less resistance to infections / cancer etc.