I don't see why women don't play 5 sets like the men. After all, women do tend to have a lot of stamina, whereas men tend to be fast and furious. I know this as I once entered a half-marathon. Setting off, I was quickly overtaken mainly by men for the first 2 miles. As I was 2 miles away from the finish line, I overtook alot of the men that had passed me by earlier.
I have always wondered why they don't play 5 sets...it's not like they cant do it!