I can name you a dozen reasons off the top of my head why we don't need in-game voice comms. Here are just a few of them.
1. The primary demographic that's going to use voice comms is salty nerds telling you how **** you are at the game and trolls blasting racist slurs, Hitler speeches, and ridiculous music for everyone to hear.
2. Due to reason #1 or whatever other reason, most of players are going to keep voice comms on permanent global mute, which defeats their purpose for random teams.
3. As pointed out earlier, decent randoms know what to do even without comms. The opposite is also true: if the player isn't very good at the game, comms are unlikely to help them.
4. Taleworlds' janky servers can't handle the game's basic functions most of times. What tells you they can handle the added load of voice streraming?
5. etc., etc., etc.
What I would personally appreciate way more (if technically possible) is a fuller integration with Steam, so that, let's say, if I met a guy named Alex and wanted to friend him on Steam, I wouldn't have to sift through 900,000 Alexes to find the one I need or seek some other way to do that.