My guess, no public dev to put a face to, so lack of trust.
Why doesn’t nostr:npub1tm99pgz2lth724jeld6gzz6zv48zy6xp4n9xu5uqrwvx9km54qaqkkxn72 have a lot of users? It already has this functionality plus a built in ecash wallet and nostr following feed.
Discussion
All the code is open source
Which is good. But who are the devs? 🥷
The most popular clients have public devs who build relationships (and therefore trust) with their users.
Skin in the game.