Two reasons: a major one and a minor one.
The minor one is that Discord is a shitty inforepo (ask me about my ongoing war on software developers who think Discord is an adequate substitute for a ticket tracker, or even worse, for all documentation), and having my impromptu lore decisions and relevant explanations scattered across distributed text soup was a giant pain in the ass.
The major one is that real-time communication (and especially Discord) aggravates my depressive disorder and volition/attention issues manyfold, and for the good of my mental health, I have exterminated all things real-time and not beloved from my life.