Actually part of it is market, too.
I mean, part of the thing is how much you would pay.
I would pay more to see Johnny Howard strip himself naked, bury himself in shit and flagellate himself with broken bottles dripping in scorpion venom than seeing, for example, ND do the same thing. (sorry mate - everyone needs a hobby)
So, do people pay more to see women or men play tennis? I dunno. Would I pay more for a black female lesbian sort my mail or a crippled male war vet? Is this a choice I can make?
Would a boss take a punt at some woman who can do the job but might just might get married and drop a bundle or some less able man who ain't going nowhere soon. What would be the best investment on average?
Why am I even asking?
To tell the truth, justice, fairness, and rights don't enter into a lot of things they are forced into. Why should I, as a boss, take on someone who I feel, for any reason whatsoever, is less able. It's my money. I should be able to pay who I want what I want.
Stuff mediocrity up the bunghole.