Can you please tell me if there is any hard and fast rule that only a single drummer can be there in any band? I know most often we find bands with one drumming set and a single player. I completely agree with your reasoning for this as well. One thing I would like to add is that a single drum can bring out the desired beats at the desired decibels. So there is no need to add another.
But have you witnessed any band with multiple drummers? I think I haven't...