Sorry, but evolution does definetely
not abolish 'anything that is useless'. Indeed it just gives a smaller chance of reproduction to individuals who carry 'features' that have a negative effect on survivability.
Any feature that is 'positive' for survival within the currently existing environmental parameters is passed on more often.
Any feature that is 'neutral' for survival within the currently existing environmental parameters is passed on more often.
Any feature that is 'negative' for survival within the currently existing environmental parameters is passed on less often.
This makes a very big difference, because it guarantees diversity, which again is desperately needed once the environmental parameters change.
'Neutral' changes that do not hurt, are traded on and might become 'negative' or 'positive' once the environmental parameters change.
This is, for example, why we (and lots of animanl species) enjoy such a lot of 'unproductive' sexual behaviour that, according to the maximising and optimizing ideology of popular ideas about evolution should be erased from the gene pool.
What a luck! Because otherwise none of us would be here
The remains of body hair on human beings are without doubt to send optic signals to mating partners. With other primates, like chimps and bonobonos, females show sexual availability with swollen genitalia. This became somewhat unpractical with the walking on two legs thingy. The primary sexual organs now were less visible, while especially the front and back view was much more prominent. This stimulated the development of secondary sexual organs (breasts and buttocks) and this funny little triangle pointing like an arrow to the interesting parts.
That's the biological signals that try to shout shout: "Hey there! Have sex with me!" (and certainly not "Hullo, how about spreading our genes?' as prissy biologists say).
But again (see neutral features) there is always a considerable number of individuals that react differently (no thank, I don't like big tits) or to different signals.
End of lecture, thank you for subscribing to Prof. Dr. Zungi's Online University, I'll send you my bill.