I can only speak to my own experience here, but I use Discord because:
- It's easy to onboard non-technical users.
- It has a huge existing user-base.
- It's feature-rich but with good UX so it doesn't feel overwhelming.
- Voice calls are consistently high quality, even with people that have bad connections.
Gamers have a history of amplifying each others' displeasure with things; if the platform wasn't better than the alternatives (TeamSpeak, Ventrillo, Mumble, etc.) they wouldn't be using it.
- It's easy to onboard non-technical users.
- It has a huge existing user-base.
- It's feature-rich but with good UX so it doesn't feel overwhelming.
- Voice calls are consistently high quality, even with people that have bad connections.
Gamers have a history of amplifying each others' displeasure with things; if the platform wasn't better than the alternatives (TeamSpeak, Ventrillo, Mumble, etc.) they wouldn't be using it.