What is needed is more men who dance. Another topic, really, but true.
If more men danced, more women would have regular partners, pro-am would not be needed,and the pricing structure would change to fit the market.
but you are missing something. Its in the Pro-Am topic and that is that many women do pro-am by choice. They don't want an AM partner.
Reasons vary of course, but one factor is independence and calling the shots. Even if the AM male is a perfect partner, you have to compromise (usually you have to give a lot more than get). With a pro you get a fully trained partner, dance when you feel like it, go to the comps you want to go to. So if you can afford it it sounds pretty attractive.