Ya I guess existing NIP-5 is on 3rd party servers. It would be hard to log usernames.
I just don't see NIP-5's purpose. Everything runs off NPUB anyways (to my knowledge?). Seems like a needless confusion point. Just delete it.
New user gets bombarded:
-NPUB
-NSEC
-NIP-5
-Lightning address
-LNURL
-Username
Many newbies abandon because of this load, and the unclear difference between all of these.