To add to what Eden has said, I used to race, but my last race was over 10 years ago. Not much has changed since then, I guess. Some observations from back then, that may or may not still apply (but since you're looking at it historically, it may be relevant)... I was a Cat 3 and was near qualifying for Cat 2 status when I quit. Even at that level, event organizers offered only non-monetary primes for the women. I won things like shoes, jerseys, etc. but locally (midwest), there was not enough participation to warrant cash prizes for the women. This lack of participation was due, in part, to what Eden has said. There is not even a women's master's classification for racing, which means that older women, who may NOW have the time to train are not going to race against young, fast riders. Being lumped all together is a detriment to the sport for women. It's also dangerous for crit racing. Crits are tight, fast, and require good handling... putting rookies in with women who are Cat 1 - 2 or even Pro makes it very dicey.
This is how it was THEN. It sounds like it has not changed, which is very frustrating because I would have thought that it would have in the intervening years, especially with such a rise in the popularity of the sport.
Actually, in the midwest, I would say that Mountain Bike and Cyclocross racing are perhaps more welcoming for women. Mountain biking races I have seen have a little more separation of categories, better participation, and cash prizes, which all make it more enticing (thus better turn out). I was just at a cyclocross race, which had a really nice cash pay-out for women. Good to see that!
The bicycle has done more for the emancipation of women than anything else in the world. ~ Susan B. Anthony