I agree there's a lot of use cases standing around with people after you've won (sitting there around players who have decided to be friendly - you both have won the engagement). You can talk, trade and do a lot of things. In this case, the presence of VoIP instead of text is not critical. It adds to the game, but it's not critical. You can do all the trades, someone can emote a yes or no, and so on. The VoIP was only critical in establishing the win or loss, or stalemate, of the situation. That instant communication was powerful. So although it seems like the VoIP is used, it wasn't that critical after you established another player as friendly who wants to trade for example and you go on playing out that encounter.
And yes, VoIP can be very useful and powerful but also very negative and so on. Already people are saying "make sure I can mute people" and so on, and "it should be opt-in instead of opt-out". Why develop something people have to opt-in for? That's my main point. The time spent creating these systems doesn't add enough to warrant the benefits. Someone who has muted all VoIP is not going to benefit from you yelling in your mic at them.
As far as dev factions and large groups; they will almost always evolve to using third party software after forming a group. It's also good to see text, where you can scroll back and see someone is recruiting for a mining run leaving in 30m, and you missed the voice call to action because you weren't around (and yes I understand both can exist in tandem). That mining run will send everyone to third party software to be in the same comms. It's only a unique feature in the immediate moments of winning a fight, losing a fight, or stalemating a fight "talking shit". I don't see it worth the time to develop if instead we're given similar instant-forms of communication like emotes and so on which can convey meaning to players.
In games without voice, like Smite for example, the "VGS" system is used heavily and most people use it over the third party voice systems that arose. For example, in that game, Curse developed an auto-matching third party voice chat, where players can be automatically in comms with their team. It got very little use, and I understand, different game, but the dev time would have been wasted if the game devs made this instead of a third party. This is possible for Starbase most likely, a third party automatching, where groups can be auto-joined into a voice chat if they choose to join in. It's not something the devs need to spend time on solving in my opinion. I think dev time is better spent developing depth for their game in adding instant forms of emote communication, rather than VoIP.
Sure! It's a lot of fun indeed! But it does not replace the need for VOIP.
I just don't see it as a 'need' for an MMO where 98 of the nearby 99 players don't really care that you're talking to that 1 person. It's much different in the MMO setting. There is value in it, I understand the value, I just don't think it is a 'need'. WA showed me how little it was used outside of messing with someone either after winning the fight, or after losing the fight. It's only convenience in roleplay otherwise. Likewise, many other games have shown they can succeed without VoIP without any issues, so I'm defaulting to it not being needed, and not being worth the development time.