Because the Sombrero thing is fun and the NOT.DEAD. is fandom being in denial about something that happened that they didn't like so they pretend it "didn't happen."
Well, it happened in a holodeck program reconstructing events from two centuries in the future. The novel line has already shown how those events really
played out, and it's a bit different. Not to mention more intriguing.
I don't read the novels.. Sombreros are fun and canon.
Not. Dead. is kinda silly. Braga killed him off in TATV. It happened.