There are many reasons behind the diversity in body hair on men. For those who do not shave,
or otherwise remove body hair via waxing or laser removal,
it is mainly a product of two things: Our ethnic heritage and the level of Testosterone.
Many men of certain ethnicity are naturally very hairy.
Even their cocks can be covered in it.
(Though why any guy wouldn't remove it is beyond me.)
Others, like me for instance, have low levels of Testosterone. My issue is caused by childhood illness (Mumps and Scarlet Fever) which resulted in small testicles and very low levels of Testosterone. This is proved out by the fact that my father was naturally hairy, and my brother has quite a bit of body hair while I do not.
Many man like to trim the pubic hair for aesthetic reasons. Personally, I trim the pubes
and shave my scrotum and the shaft of my penis
because it is less sweaty and, therefore, less itchy - and I prefer the well-groomed look of it. And, let's face it - when I was a dancer it was a requirement that we have no visible hair, and I got used to it.
Whether you're naturally hairy or smooth, or shave, wax, or laser it away is all a personal preference. We do what makes us feel good about ourselves; perhaps going for a look we like on others. Or what our partners/spouses/significant others prefer.