NIP 04 is used all over the place still, including DMs, can you describe what you're seeing in more detail?
One real world scenario I encountered while testing coracle is that if only nip-44 is implemented this is not backwards compatible with nip-04. Not sure at all about NIPs best practices, and if this is best addressed at all in NIPs, SDKs.
I think nostr:npub1jlrs53pkdfjnts29kveljul2sm0actt6n8dxrrzqcersttvcuv3qdjynqn had thought this through on coracle, and there was some bug he squashed to make these DMs NIPs compatible.
Discussion
Coracle handles backwards compatibility to nip-04 fine, no issues with Coracle.
I mentioned to Terry that some apps may still use nip-04, and not nip-44. Therefore if new apps build only nip-44, without taking into account backwards compatibility this would be a nostr interoperability or #nostrability pain point.
Ah yes, it certainly would