It may be an issue of having multiple channels of communication, and the bug tracker is only one of them.

For example, though I work for Mozilla, I'm not terribly good at keeping up with the mailing lists, so every so often something pops up in Bugzilla (which I read more frequently) that seems to have come out of nowhere.

And of course stuff happens in our IRC channels that never makes it to a bug; same with internal emails. There's a lot of effort involved in making sure your communication is clear and accessible when you have several different modes of it.