Besides, it is waaaaay more fun to be the "Super uke". It is also better for you (as nage) to "handle" this much more pressure.
One of my partners in our dojo is an ikyu in the count-down for shodan, he is getting as quick and pressured by uke as possible.
What fun......ukemi is so much more interesting when you are pushing their boundaries.
But then, that is just my opinion.