Huh? Becuse it is "the lore" that is how it have always been, that how the world and story was built. For several years at that, The lore should always stay as it was. You cant just change it at whims. It is kinda hard to take the story seriously if you cant even trust it anymore. It is like should we even take any events from Legion/BFA seriously if if we just think they gonna recton it in 5 years and it have never happened.
I do look forward to play shadowland and it looks promising for me atleast, But i really dont like Retcons.