As an example, I've been bugged by YouTube videos suggesting I need a good quality pubic hair trimmer. The idea of shaving my pubes has literally never occurred to me until this advert started telling me it was the thing to do. I happily say I remain completely unconvinced, and short of requiring some sort of groin operation I intend to keep cutting implements far from my genitals.
It's all fun and games, until your crotch forest gets so thick, that you are getting ball hairs tied around thigh hairs, and then you sit down and move your legs in a way that makes your hairs yank themselves out from both directions. Really hard to explain the high pitched yelp of pure pain at the office when that happens. Aside from the reason those commercials give you as to why you should do it (namely getting pussy), I have found, when I've done it, the following things happened:
1. That it's far more comfortable overall. I get less hot down there, which given I live in Alabama, where the average forecast is "Fucking sweaty hot as balls for the foreseeable future", to actually reduce the level of that "hot as balls" on your actual balls, is pretty nice.
2. The above mentioned "you don't get tangled crotch hairs that violently yoink out at inappropriate moments.
3. Less risk of dingleberries, assuming you are lumping all downstairs grooming into the equation.
4. Your junk looks bigger! This is really only important if you are in a situation where you have someone to show your junk to, but not having all that foilage down there, does make your dangly bits seem larger under observation.
5. More sensation and enjoyment down there, from people playing with your one eyed samurai!
6. Linked to 5, less complaints from lovers if they are giving you downstairs smooches, of getting hairs stuck in their teeth! I personally have never had this, as I'm not a fan of receiving oral, but I am a fan of giving it to my lady friends. And them being trimmed does make that past time far less...dental flossy.
So I assume it would be similar for them.
It can be a bit of a pain to maintain it, I never had equipment specifically designed for it, and just muddled through with what I had. But the results were quite positive.