I'm not well versed in their history wrt bitcoin, but my impression is that they're only useful as a mnemonic. Fine for certain bitcoin applications, but how many people are memorizing their nsec? Apart from that, they're just a string of characters which in most cases only increase UX friction since apps usually force you to enter each word individually. Just use ncryptsec, which actually protects the key, to move things from app to app, and bunker sessions to actually use the key.