I think the concept of canon is very useful, because it's a consistent starting point for discussion. Exactly how strong and binding the canon needs to be can b

I think the concept of canon is very useful, because it's a consistent starting point for discussion. Exactly how strong and binding the canon needs to be can be debated, and varies depending on the situation. The term largely descends from its use in Christian scriptural politics, where early church councils had to pick which documents were going to be considered true and the basis of their faith and which weren't. In this case, deciding on a canon of scriptures was important because it defined their religious teachings and what it meant to call yourself a Christian. ...but really, I come at it from a fan works perspective, and I just think it's useful to at least know how you're diverging from the shared understanding when you create something. Even your Truce at Bakura example relates to there being a Star Wars canon, it's just that we can accept that there's nested variants of it -- the original movies always holding primacy, and then either layering Legends or the Disney properties on top of it. Having no concept of a Star Wars canon at all would leave us with something like Star Wars: Visions, where "Star Wars" is more of a vibe that stories are inspired by than a setting that stories happen in.