It's not just females; males do the same thing. It's all a matter of personal grooming preferences. Some prefer to shave, some prefer to trim, and some prefer to leave it untouched. Some think it's more natural to leave it untouched, and some think there's nothing unnatural about shaving or trimming pubic hair just as there's nothing unnatural about going to the barber for a haircut or shaving one's head. Some do it because they like how it looks better, or like how it feels more comfortable, or because being shaved smooth makes them feel even more naked.
Also, shaving, waxing, and trimming are not just naturist/nudist activities. There are a great number of non-nudists who remove their pubic hair to some extent. There's absolutely nothing wrong with trimming, shaving, or waxing just as there's absolutely nothing wrong with leaving it untouched. Female or male, nudist or textiled, smooth or bushy, to each their own.
naturist since 1990