This will probably earn me some sharp criticism but I'll say it anyway. Boys and girls from a very young age are into entirely different pursuits. Maybe it's in the genes, maybe it's in the way we bring up children. My 5 y.o. grandson loves machinery. He loves cars and trucks and big machinery and trains. His 7 y.o. sister is into dolls and clothes and colouring pictures. It's the difference between masculine and feminine. That's not to say there aren't exceptions, however. Many boys pursue careers which some may consider "feminine" like interior design, fashion design, cooking. And many girls pursue careers which some may consider "masculine" like construction, welding, carpentry, driving those big mine trucks. There's nothing wrong with people pursuing careers in fields which many consider gender-specific to the opposite gender. Many of the world's top chefs and fashion designers are men. When my eldest granddaughter was in her pre-teen years she enjoyed doing carpentry, construction work and using power tools. She has helped me build the framework for my layout and has helped me paint more than one room in the house and could patch holes in drywall as well as I could.
I think you're right that most women would rather support the hobby than actually be model railroaders. Many times in articles in MR I've seen statement like, "My wife painted the backdrop," or "My wife made all the trees on the hill." Neither my wife nor my daughter had any interest in my model railroading other than to comment, "That looks nice, dear," or "Great looking farm scene, Dad." My son has about the same attitude. However, my eldest granddaughter when she was about 6 to 12 y.o. enjoyed doing scenery on my layout but had no interest in running trains and told me in no uncertain terms that she wanted nothing to do with the wiring. She has an artist's eye and I depended a lot on her for help with scenery and detailing scenes. She was also very good at painting N scale people which I find hard to do. Now that she's in her mid-teens, her interests have turned to other things--boys, cars, fashion, painting and studying hard to get good marks for university entrance. Unfortunately, they moved away a few years ago so I seldom see her now.
These are just my thoughts, my two cents worth, on the subject. You may not agree with me, but that's okay.