Because lemmy, like Reddit, is not conducive to the concept of a megathread. It’s the format that’s the problem, not the contents. You expect people to constantly stop what they’re doing and deliberately navigate to an old megathread and then sort through all the comments/conversations happening with days - weeks even - of gaps between them? Nobody does that.

People are treating this platform exactly like reddit because the churn of posts is exactly the same. You participate in the first hours or you miss it entirely.