cottons holds its own weight in water 20 times. that makes it an excellent material for towels and an absolute shit material for clothes, unless you live in a desert. in summer it clogs with sweat and never dries, preventing evaporation which is how the body cools down. in winter it drenches in winter rain (outerwear) or in sweat (innerwear) and gives you hypothermia. there's a reason why hikers have a saying "cotton kills". the only reason cotton has become the dominant textile is that it can be produced in mass quantity for cheap (by using slave labour in China and soil-eating intensive agriculture).
the problems with cotton only grow worse for form-fitting clothing, because having a textile right next to your skin that also happens to soak in humidity and never dry is a perfect recipe for fungal and bacterial allergies to develop.