Mostly because web clients cannot create or see them due to lacking feature of web signer extensions.
I realized private zaps, my favorite kind, are not in a NIP yet? All I could find on it were these closed and un-merged pull reqs. nostr:npub1gcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqlfnj5z nostr:npub1xtscya34g58tk0z605fvr788k263gsu6cy9x0mhnm87echrgufzsevkk5s
https://github.com/nostr-protocol/nips/pull/1064
nostr:note1gtee08l4h24k43ea39z89glm85rlg4fntayuhtf27tlzlaeaqchs5fykyv
Discussion
would be nice if it was documented anyway. if giftwraps can be done, y not private zaps?