As a Bitcoin old timer I would say there are several reasons.
The various waves of bitcoiners that seem to come, perhaps with each cycle seem to have different styles, value and priorities than older holders. So partly just a culture thing.
Some of the discussions, and even fights can seem futile (I have seen threads on "wen bigger blocks" and "Bitcoin is a failure because it has a transparent Blockchain" just this morning). Some OGs might not want to relive and rehash those.
And then of course there are the opsec challenges.