From Dr. John Campbell’s YouTube channel:

When you have a fever, the body is more able to combat viral and bacterial infections.
…
If we let the temperature just ride in an adult (to say 39 degrees C or 102.2 degrees F) … that’s not going to do me any great harm but I know that’s combating the infection much quicker.

If I artificially lower my body temperature by giving ibuprofen or acetaminophen or paracetamol then what I can do is make that disease process worse, make the infection last for longer, and increase the probability of complications from that infection.

So we see that fever is a natural defense mechanism and very often should be just left as it is in adults to allow us to fight the infection and have less complications and shorter duration of illness.

Thanks to forumholitorium for introducing me to him.