It is not a coincidence that most of the various proposed alternatives to PGP (signal, wormhole, age, minisign, etc) are led by a single golden implementation and neither support nor promote community-driven specifications (e.g., at the IETF).

Over the decades, PGP has already transitioned out of old key formats or old crypto. None of us is expecting to receive messages encrypted with BassOmatic (the original encryption algorithm by Zimmermann) I assume? The process has been slow, arguably way slower than it should have after the advancements in attacks in the past 15 years (and that is exactly the crux behind the schism librepgp/opengpgp). Nonetheless, here we are, pointing at the current gpg as "the" interoperable (yet flawed) standard.

In this age, when implementations are expected (sometimes by law) to be ready to update more quickly, the introduction of new crypto can take into account adoption rates and the specific context one operates in. And still, that happens within the boundaries of a reasonably interoperable protocol.

TLS 1.3 is a case in point - from certain points of view, it has been a total revolution and break with the past. But from many others, it is still remarkably similar to the previous TLS as before, lots of concepts are reused, and it can be deemed as an iteration of the same standard. Nobody is questioning its level of interoperability, and nobody is shocked by the fact that older clients can't connect to a TLS 1.3-only server.

You're right, it's not a coincidence. The track record of standards-body-driven cryptography is wretched. It's why we all use WireGuard and not IPSEC. TLS 1.3 is an actually good protocol, but it took for-ev-er to get there, and part of that process involved basically letting the cryptographers seize the microphones and make decisions by fiat in the 1.2->1.3 shift (TLS 1.3 also follows a professionalization at CFRG). It's the exception that proves the rule. It's contemporaneous sibling is WPA3 and Dragonfly, and look how that went.