Coaches are more likely to tell women how to play I suspect. Men would pushback a lot and not want to change, and women would be more receptive to critique. Obviously Im stereotyping, but thats just what I think.
As for why they want everyone, not just women, to learn spinny serves, its because spin serves are the best type of serve. They can be ramped up indefinitely, and it teaches you variety. Also, you do not ever want to double fault, and spin serves is how youre gonna avoid it without doing weak serves.
Over the years, I've found just the opposite to be the case, ie more women are reluctant to adopt a topspin or slice (aka "spin") serve than men. The usual reasons are "I've tried to use a continental grip and can't do it"/"It will take me too long to learn and I have a match on Tuesday"/"I like my serve just as it is". I've found that men can make the basic motion necessary for a topspin more easily than women (in most cases), however it's tough for most rec level players to get enough spin on the ball to create the energy necessary for an effective serve. Most of the "spin" serves I see are just too spinny and sort of just lie there on the court waiting to be crushed.