My computer is undergoing technical difficulties at the moment. I got some sort of audio memory leak recently that crashes my computer if I leave my sound active. Probably going to try to fix it next week when I have a bit more time to toy with it.
Even if there's no voice chat going on though, the text chat is relatively active at most hours, and people can always text chat to other users.
Personally, I often find the text chat more convenient, as I don't always have earphones in, and I can come back after stepping away from the computer and still know what the conversation was and respond to it. But maybe thats just me.