I had heard rumors it was intended to be in-game but removed due to fears of trolls/immature people ruining the game experience for others. It also makes the tower seem like a big waste of dev time implementing without the ability to actually socialise, especially seeing as it feels like it's intended as a social hub (like the towns in other MMO franchises). It's also highly counterproductive from a teamwork perspective in missions/strikes. We shouldn't have to invite random people into our fireteam for the purpose of being able to talk to them, it's nothing more than a hinderance.

To be honest I dont think being able to hear/talk to everyone is such an advantage. Just because you have the people who think online play is the place to represent their rapping skillz, the place to say "hello does anyone have a mic. Anyone. Talk to meee", blast their crapy music through their crappy mic. But who knows, i do see them adding this as a feature. I just hope when you're in a fireteam you can't hear anyone but your fireteam.

I think you are going to be in a fireteam most of the time though, you're always going to want to be with at least 1 friend. For all else, the mute functionality can have a workout. I don't see the point in completely removing it for the purpose of immature people trying to ruin an experience.