Self-Sovereign Identity and DIDs are a very fast moving train. People argue that in the early internet days there was a similar competition between new protocols(compare with DID methods) before we arrive in our todays HTTP(S)-only world. Similarly DID methods will probably consolidate to a handful within few years and DID Core is only a first step to get a minimal common denominator. Also its questionable if Microsoft&Google and the others are fearing a rapidly evolving ecosystem that they can not jump on as fast and therefore remain sceptic in any case