On the contrary, if a meeting is unnecessary, you can afford to spend the time on whatever tangents and pet causes the attendees want to bring up, so you don't

On the contrary, if a meeting is unnecessary, you can afford to spend the time on whatever tangents and pet causes the attendees want to bring up, so you don't need to bother with channels and delegation. If a meeting has been convened for an important purpose, it has to be protected against people trying to hijack it for less important things, by deflecting those things to other channels and other groups. (Of course you can't get sucked into the morass of authorizing and organizing subgroups right there or it doesn't help much.)