The Wayland standard does not prescribe it (unlike X), and the reference implementations were monolithic for a very long time.

Wayland in general had a rather cavalier approach to doing away with things that X users take for granted, like, well, making screenshots. Eventually, under pressure, those in charge agreed that these features are actually very important for real users, so implementations appeared. It's an understandable way to discover the minimal usable subset of features, but the process of it is a bit frustrating for the early adopters.

> so implementations appeared

Indeed - implementations, plural. Incompatible with each other, naturally.