That's why they're different apps, they do things differently. Maybe other apps would have added support for the transcript tag, maybe they wouldn't but that's for them and their communities, no?
Discussion
Others apps can add the Airchat NIP if they want to. Yes, that’s for them to decide.
Standards are different than apps. If we all make a standard then what's the point of even making it on nostr? Why not just use a private DB on a website and enable API access to your data?