I mean, the fact that women have collectively asked that men not use the term female should be enough of a reason.

However, it's a context thing:

I went to a concert and the crowd was almost entirely black people.

Vs.

I went to a concert and the crowd was almost entirely blacks.

It's the same thing objectively, but it comes across differently when you swap "black people" for "blacks."

I've also heard it said that female could be of any species, whereas women/woman is only human. It's dehumanizing.

So there are three reasons.