It's clear why this happens and of course it's not ill intended. The mind naturally follows the most-traveled association path from a new stimulus back to something familiar.
Unfortunately, that is the anticurious direction. Swapping out a specific new topic for the nearest familiar one means replacing a potentially new and interesting discussion with a repetitive old one.
These large generic themes are like black holes: if you fly too close to one, you get sucked in there instead of going wherever else you might have explored, and then no new information emerges.
https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...