I think the largest contributing reason is that Discord is where a lot of people are these days. It's convenient, well understood, easy to add another channel.

I think the largest contributing reason is that Discord is where a lot of people are these days. It's convenient, well understood, easy to add another channel. Every time you ask someone to use a solution they don't already have, you're adding friction to connection process. If they've already got a Discord account, and the client, and just have to press the button, it's easy. On the other hand, if you ask someone to install another special piece of software to get involved, and they have to setup an account, and then verify the account - it might just be too much.