The majority of pro-shot folks I know didn’t get the first booster much less the second one. I imagine the majority of people who took multiple boosters did so because they are already in poor health and think the Rona will push them over the edge. With this data set it may be hard to parse correlation from causation.
My 80+ YO in-laws got jabbed, and were very upset that me and the Mrs. and kids didn’t get it.
Then some data and stuff started coming out, and they haven’t been boosted as far as I know.
We don’t talk about it though, because they know where we stand, but they usually tell my wife these things.