Actually the main reason is the lag between the connections...because while you won/lose the round..on your adversary screen the battle is still running...so yes is kinda annoying to wait..
Actually, the problems is because this is a browser game, u have to wait the information go to your opponent, then he waste like 40 seconds to think, then the information come back to you. 4 factors involved, your internet speed, your opponent internet speed, the speed of the urban server, and the time the players uses to think.
I thing, that it is my opponents "thinking" in 95%. May be wrong, If yes correct me.
It would be nice to have possibility to surrend from duel withought penalty, if I wait on my opponent more than 1 minute.