Wikipedia has cleanliness as "Cleanliness is both the abstract state of being clean and free from dirt, and the habit of achieving and maintaining that state. Cleanliness is often achieved through cleaning. ... On a practical level, cleanliness is thus related to hygiene and disease prevention".
Maintaining cleanliness is important for our self-confidence, physical and emotional well-being not just attempting to impress a potential play partner. The main purpose of hygiene waxing is just that, to maintain hygiene. It's a lot easier to wipe a smooth bottom clean than one you can't see for the hair. On the front side, yes, a well groomed willy will look bigger simply because you can see all of it, but there's also the feeling of being clean, smooth, a reduction in odours and best of all an increase in sensitivity.
Images are for the purpose of illustrating treatment areas only and are not intended to offend or sordid purposes.