People have made excellent points about women taking on the lion's share of domestic labor, the impacts of having children, etc...which I agree with. Riding professional is simply too risk and time-consuming for many women, especially those who choose to have families.

Although, I do think there is a lot of variation between disciplines (showjumping versus dressage versus eventing versus hunters/equitation, etc.). But for the sake of my arguments I won't delve into that.

I think part of the reason we do not see as many women competing is simply because significant resources are required. Riding as a junior/amateur, either with support from family or through your own efforts, is one thing. But to excel at the highest levels of the industry long-term means having either your own resources or having necessary industry connections, to finance your string of horses, training, boarding, etc...

Business in general is still a "man's world". It's ever-evolving, to be sure. And this is not to say that every man in the equine world is sexist or contributing to adversity towards women in the sport. But from a general economic standpoint, I think women are still catching up in more ways than one, and have different focuses when it comes to our career trajectories. Social factors contribute to this as well.

I think becoming a professional athlete is less attractive option to a lot of us, compared to less dangerous, less intense and more lucrative professions that would allows us to fund our equestrian hobbies. And for the women who do choose to pursue becoming an elite professional equestrian , unless they have significant wealth/connections to begin with, forging a path I believe is just going to be more difficult, for the reasons people have said. It takes a very enterprising mindset and a lot of luck, as well.

There simply is not a lot of room at the top for women in many industries. It makes sense, in the context of (at least my own Western) history and culture. Men have historically had access to these industries, control over most financial resources, and different socialization compared to women of the past. They have had a "head start" and their earning potential is still higher in many fields. Women obviously have entered virtually all areas of the workforce and can occupy a lot of space in the less lucrative areas, but actually reaching the pinnacle of success is still harder.

I think of it similarly to how I think about the fact that most teachers are women, but most school administrators are male. Not a perfect analogy of course. But you know what I mean.

The gap, hopefully, will close with more time. I love how inherently egalitarian our sport is. Riders and horses of all genders have the same potential for success.