In my post on the Hugo winners I commented that few of the finalists in any category had I even heard of. Tis is quite a change from years past when I was familiar with the work of all of them and knew many personally.
When did I drop out? I decided to trace the history of one category, Best Fan Writer, as the one where my acquaintance was the closest. And I found that from 1980 to 2012, I rarely knew personally fewer than three of the finalists (and when it was less, it was two). Some I knew very well, others I'd just met or briefly corresponded with, but I knew them. One year, 1989, I knew all of the finalists.
But then it abruptly changed, and from 2014 on I've known only an occasional finalist. All the others are completely unknown to me. That was just about the time I ceased considering myself an active fan, and that may have had an effect, but I don't think it's the whole story.