Yea there are a lot of people I follow who were fairly active before, but haven't been now for a while. I think people will just naturally spend their time where they find others they want to spend time with, or more generally where they find content/activity they like. I believe as nostr continues to make it easier for people to create/publish content, as well as to find and connect with the content/creators they like, then it will naturally draw more people to use it, and then I becomes a domino effect. For now though it seems like a lot of people would rather keep going back to other networks. I think it will keep improving though.