I remember moving to mumble from teams peak because it allowed pretty cool levels of configuration.
Back in the late 00s and early 00s I was doing world of warcraft raiding. I had the server setup to have one key for main raid and another to talk to only officers. Quite useful especially in bigger raids.
Also as I recall for any remotely large ts server you needed to pay. The self hosted one was always gimped. Mumble you could self host with no limits.
For a group our size (we regularly have over 800 people on our mumble, peak is somewhere around the 1.3k mark if I remember correctly), it would also be very cost prohibitive to use TS