Canon is messy. With Star Wars, for example, I see the original film, and then tons of different story branches going out from it in different directions. Sometimes they cross at other movies, sometimes they drift off into the EU before tapering off into nothing, or fly off into my imagination. There is no set canon universe(s). Trek, on the other hand, has infinite headcanon universes that range from encompassing every piece of Trek media I’ve ever consumed, to being fairly empty, and anything in between. Why do I compartmentalize fictional universes in my head like this? I have no idea. I just… do, I guess.