This thread has a great point, in every siege I've been in there's just not enough time to prepare.
As for the attacker getting bored, that is very true; but if they had plenty of stuff to prepare in the meantime (camp manangement, ect) it should last them at least a minute or two.
Afraid that's all I've got, but I'm glad to hear that the time got changed in today's patch. (it did get changed, didn't it?)
That was so funny, I laughed twice.