I would interpret that to mean that there weren't enough that were still coming to the reunions.
I went to my 20th, and that was it. I was glad I went, but I wasn't interested in making it a regular thing.
One of the things that surprised me was that the high school cliques still seemed to be in place. I figured that we are all adults now and would interact on a different level, but the people that wouldn't want to talk to me in high school didn't seem interested in talking to me twenty years later.