In answer to your 2nd question, because people who want to make successful clients understand the need to include features that the market demands!
There is little to no demand for zaps except among bitcoin bro devs. 99.999999% of anyone who uses the internet hates crypto, let alone second layer centralised KYC crypto. And only 1% of the 0.0000001% that do want to use zaps actually run a node. Zaps/bitcoin are actually just putting average people off Nostr.