Fact 1 - sexually active people subconsciously look at peoples’ crotches when meeting them.

Fact 2 - evolution doesn’t fine tune things if they’re good enough to get the job done well.

So the fact that pubic hairs are unsightly crazy-looking things might not be because they are fine tuned to be like that - it might just be because they do their job well enough and they just ended up looking like that.

What job could that be?

To confirm visually that you are sexually mature.

That may literally be it - a localised fuzzy indicator of whether or not you’re able to make babies.