Same reason why women like having women spaces. There certain experiences exclusive to being a male.
There are no women only spaces where I live. Nor were and no one complained. Unless you talk about monastery of toilette.
Example?
Talking about your feelings without fear of a woman getting the ick.
And so what? Given the display of men's feelings w.r.t. to "mixed groups", I (heterosexual male) get the ick about some people here... For me most of it is about the space/relationship where certain things should happen, but I guess scientific misogyny is a thing too.
Why so toxic without understanding (and caring to understand) the other side of the discussion?
Plenty of full explanations in this thread.
Cigar smoking.
I know of an older woman (has grandkids) who smokes cigars at the cigar shop I smoke at. The discussions with "The Boys" are different when she's around.
I'll have to let my HR manager know women can't smoke cigars. She clearly doesn't know, went through a bunch at our last company meeting.