Why did our evolution do away with the cloaca, or a similarly functioning waste disposal orifice?

The cloaca seems like it would be something we'd keep around. Many mammals still have easy way to deal with no wiping. Complete amateur here, but it seems like it would keep down disease.

At the same time, the cheeks on our bums cushion our pelvis bones. Also, there's lots of muscle there, so perhaps that's why?

Thanks.