Communication actually matters in sim as by design many of the systems that are present in RB and Arcade are not present. Currently sim players have a sort of agreed-upon system of menu voice lines that ping the map in order to communicate, which is pretty limited to say the least.
The voice chat would only be in sim battles, which is a community of players within warthunder that I think are a bit more mature and should be able to handle such a feature. Obviously, it would also be optional so if you don’t want to hear a bunch of nerds yelling at each other to stop shooting friendlies that would be a possibility.
Personally I would love to be able to speak to ground units while flying a plane that I spotted something and where its at, right now that would require me using my keyboard and its just a mess and not even worth the effort.