For those who endure tepid climates, it may be a stretch to say that polyester is the only fabric that holds its shape no matter how many dewpoints it's forced to endure, and quite aside from the relative altitude of mercury in the graduated beaker below the stairs.
Certainly, cotton has its place, whether that's poolside, dark side, or actively displacing volume in the kidney-shaped receptacles we fall for, headlong and fully clothed, at the end of a hot and bothersome day.
Should polyester be allowed in the jean pool? Don't make me laugh. I'll give up my soulful threads of shrinking violet when pigs fly out of my lipstick, in formation, and on a heading of 29° 12' north by 70° 10' west.