Most guys I know, fighters and guys who train in casually included, are not interested in seeing girls punch each other. A lot of guys can handle girls grappling, but it's a whole other thing when you add striking in. I've heard promoters say things like, they'd only consider having a women's match if there were no knees and no elbows, cause they don't want to see a girl bleed. Or they simply don't respect that women can be skilled or entertaining to watch.
You add that on top of what you guys mentioned, lack of depth of talent pool, and it's an uphill battle for women's MMA.