Hmm I have noticed this concern gets hand waved away as nothing. This makes me think this will forever be a niche thing.

Command your whole identity with a single key, but a single rogue app, or someone getting access to it somehow, and it is lost. People have a lot of energy and time tied into online identities. Being able to recover from lost or compromised keys is essential I think. Hopefully some work is done on that, I think a solution is necessary for Nostr to succeed.