Why? you ask. I'm a lady with boobs and hips and things, and male dress forms don't come with those.
That's true. And if you can get some kind of custom dress form to fit your shape exactly, definitely go for it. But if you need an adjustable dress form, either because you're building garments for corseted shapes or because you expect to work for variously shaped clients - consider a male form.
When I was a wee seamstress my parents bought me a dress form, one of those adjustable ones that gets larger and smaller by the use of these little turning gears. And it's totally fine if i need a basically human shaped clothes horse, but LET ME TELL YOU, it has nooooothing to d with my actual body shape! Chiefly because the boobs are these little hard immobile mounds which are too high and too close together to even approximate my own chest-age - but also because even adjustable dress forms can't be every possible shape.
Like, if the chest is a lot bigger than the waist, the dress form strains and eventually stops adjusting. The "adjustment" has to fall within a certain range of bust-waist-hip ratios or the thing might break. And I have really no idea how those tiny hard immobile boobs relate to the shape of a large busted woman -"yeah, the chest is 40 inches around, and the apexes of the boobs are wierdly far apart and somehow shaped exactly like the cup of a 32 B" - like probably not?
But with a men's form, you can use batting and padded-out undergarments to build up the shape of your own particular body, and get the fluffy parts and the places in between all just right - and sqooshable, because batting with squish under a corset or whathaveyou.
Just a thought.