In a classroom, the boys will often be louder and take more space than the girls. Well, adults can be just as bad, at least if kids are around.
The other day, I organized a game for a group of 20 people, about half adults and half kids of various ages. When some kid asked something and I was about to respond, one of the adults interrupted me. I hadn't coordinated with him, and he used a voice that clearly was not asking or suggesting: he was telling the room how the game should be played.
I didn't feel like interrupting him - perhaps I succumbed to his authority? - so we played by his version. It was slightly more complicated and caused many of the participants to not be able to see what was going on. Therefore, the players gradually shifted to the simpler version, my version.
Adults seem to believe they're the authority, even if someone else has planned everything out. Sure, it's alright if what you say is important for everyone to hear, or if you have some intelligent explanation that lets everyone understand. In those cases, interrupting might be warranted. But sometimes an adult just likes to hear their own voice and wants to do things their own way. And they have the power.
I'm probably no better, but it sure is annoying when someone else does it.