I think we've gotten better at compartmentalizing our conversations. When IRC and AOL chatrooms were big, the idea of online communication was fairly new. Nowadays, most people can handle the concept of asynchronous chatting with ease-- being able to follow multiple, non-real time (in the sense that you aren't forced to listen to the person at that moment in time-- a chat line can be read instantly, or when you're done with what you're doing) conversations at the same time.
To that end, most people don't even think about having group chats. They compartmentalize what they're doing into single units of required information, and then go to each person they need that unit from individually. Let's say you're having a party at Bob's place, Jill is bringing the food, and then you're meeting at the movie theatre at 6 beforehand. It's almost an ingrained reflex to converse with Bob in one chat window about cleaning up beforehand, while talking with Jill in window 2 about how many peppers to use, all while telling Alice and Eve to hold on while you hammer plans out in windows 3 and 4.
And the thing is, while this seems inefficient, from the side of who needs to know what, it's actually simplified. Bob doesn't need to know what kind of peppers are going to be in the food in order to take care of what he's doing. Neither does Jill need to know the details of which cleaning crew is going to be at Bob's before the party. And all Alice and Eve want to know is which movie theatre it is and how late the party's going til. For the most part, 1-to-1 communication does what we need it to without being overwhelming (as the chat window would end up being if we had Alice, Bob, Eve, and Jill with us in the same IRC channel).
Which isn't to say there aren't situations wherein having groups of people are useful. But those are generally defined as "meetings", and there's both explicit and unsaid rules that usually pertain to such things-- there's a point to the meeting, an agreement to not speak over each other, a meeting leader that has a syllabus to follow. You're not going to have 3 separate conversations going on where 2-3 people of the 10 at the table are talking across the table to each other during the meeting. And any meeting that doesn't have this sort of order imposed on it ends up being a waste of time, because no information gets passed on and nothing gets resolved. All you end up with is a mass of chaos wherein you have to tease bits of meaningful conversation out in a process roughly equivalent to trying to get a pair of headphones out of a ball of wire that's been sitting at the bottom of a desk drawer for a couple years.
tl;dr: I don't think it's a software issue so much as it is a wetware issue-- meaningful unstructured communication gets exponentially more difficult when more people are involved.