Not everything is an evolved functional trait, like the first poster was saying.
Loosing our hair and getting greasy was a functional adaptation. That grease getting stinky is just a byproduct that didn’t introduce a negative selection pressure.

Evolution doesn’t have a plan, it just takes the shortest path towards better that doesn’t make things worse.
Giraffes have a nerve that runs from their brain, down to their torso, then back up to the top of their neck. There’s no reason or benefit to this, it’s purely because when what the nerve runs to evolved in reptiles, it was at the top of the torso. Neck gets longer, nerve follows since there’s no pressure to select against stupid nerve layout. There’s a species of toad that evolved to become so small that their ear bones can’t actually pick up the sound of their species mating chirp. They still chirp, but none of them can hear it, and instead they signal based on seeing the motion of chirping.