The space in the male abdomen that would house the uterus, ova, etc. in females, what is it used for in men?

Storing beer.

Fat cells.

It’s a storage place for men who have large penii. Rather than hanging down, it collapses and retracts into the abdomen, somewhat akin to a kangaroo’s pouch.

Looking at this from another angle:
Relative to men, women have bigger pelvis bones which likely offer more space for female parts. Men don’t need that space so they have relatively smaller pelvis bones.

A womb with a view, the belly button used as a rudimentary peep-hole.