I suspect that some people don't want to read something that's non-canonical because they feel like the emotional consequences of the stories will be rendered moot, which undermines audience investment in the stories and undermines verisimilitude.
That's a far better phrasing of my attitude than anything I ever came up with. Thanks, Sci.
(It's not that I won't read anything non-canonical. But I definitely have preference for Trek
books that fit into the Marcokradiverse. The lack of emotional consequences is precisely why I didn't find Crucible
Which, to be honest, is not something I can experience myself -- I found Crucible
to be a powerful, emotionally moving experience all by itself, in the same way that I might find, say, The Once and Future King
to be a powerful novel all by itself, without needing a sequel for it to fit with.