A combination of personal preference, and just how much I despise what they’ve done in terms of making information hidden away from the internet - anything on Discord cannot be indexed (and there is no way as a server admin to allow indexing as an opt-in capability), they’re just another big platform that is waiting till it hits critical mass to then start turning against its users (in my opinion).
Oh, and the fact that they couldn’t care less about the Linux version of their desktop client (which is riddled with issues due to being on a grossly outdated version of Electron) also doesn’t sit well with me, but god forbid you try to develop or use an alternative client… In a way, just like Reddit now I suppose.
Unfortunately, unless all of your friends are in the FOSS world, it feels useless to even entertain the idea of convincing them to switch to something else. Just another case of the “Network Effect”…