Every minute spent dealing with a chat server is one less minute working on your project, or spending time with your family.
With discord, I could use those time working on the project!!!
And it saves all the history, which slack puts behind paywall.
Also, it has neat features like conferencing.
Some of the OSS I follow do nice QAs, presentations, etc on Discord, that just didn't happen or was unfriendly.
I've been on Zulip, Matrix, Libera and Freenode before, discord is simply easier for users and admins.
With discord, I could use those time working on the project!!!