It's a conversation, not a competition

I've posted about this before, but it just keeps happening so I thought I'd gripe again. What is it with folks that feel like they have to be louder than anyone else around? For instance, the other day out at a restaurant there's a group of three fellas having lunch. The ambient noise is at a reasonable level, when all of a sudden these guys start trying to talk at the same time, and as one gets louder, the other one ramps up his volume. Before long it's like being at a Who concert, exceptin' it ain't music, and it ain't something I want to hear. I see this all the time. It's usually worse at places where you have to speak up even to have a conversation, but it happens often enough just about anywhere that's not too formal. Why not pause and allow the other person speak and converse in turn? When did it become acceptable to just try to outtalk the other? Is there a competition I'm not aware of? Will the loudest guy win? What's the prize? For these folks I hope it's a balled-up sock in the mouth.