This is a feature which wasn't fully implemented originally and I'm not sure if it should be implemented now. It wouldn't be hard to add, but I was never the fan of adding tons of very small details which all require additional mechanics.
Viewing post in How to Change Pubic Hair ?
https://itch.io/t/572003/pubic-style-customization-release-v1-for-strive-0525
There's a mod 0.5.25, that allows you to change the pubic style. (Allegedly, I haven't tried it yet.)