I imagine part of the problem is that not everybody is ready to read a longer piece at the moment they see it.
The good thing about Nostr is that feeds are chronological, so there's no risk of "losing a post to the algorithm."
For instance, I intend to reply to your Substack posts, but I want to give them the proper time and attention, so I'll end up going back over them and commenting later. Hopefully with reposts we can re-up conversations for others to jump in.