Gaming was the original use-case because historically every gaming clan had a teamspeak server, a forum, and an IM group chat, each of which was a pain to set up and administer. But it just so happens that this is also a pretty good set of features for basically any kind of small-ish online community, so it's taken off across a huge number of areas (my hot take is that feature wise it's actually better than Teams/Slack/etc, especially in terms of how the voice call UX works, and inertia and general reputation/theming are the main reasons it hasn't taken off for internal company communications).