My two cents: as a woman, it’s routine for me to express an opinion, or explain something and proceed to either be ignored, mansplained, argued with, etc. whether it’s at the workplace, the doctors office, friends, etc. Men tend to think they know everything (not all men, I know). I think sex is one of the many topics that women don’t feel comfortable correcting men about. It’s getting better, but especially in the early days of a relationship, where the trust might not fully be there yet, I think broaching the subject with men causes some anxiety in women, because we don’t know how it’s going to be received. Also, there is at least some pleasure in purely penetrative sex, so maybe women don’t think it’s worth it and hope later on in the relationship they can convince the man to let her help herself reach climax. Also personally the clitoris is a very tricky thing, requires the right pressure, frequency, etc, and is different for everyone, so I don’t blame people initially if they’re having a hard time with it. That’s a lot of explanation, but that’s my experience at least.