Speaking as a young woman, my hair is very curly, and I don't straighten it because it makes it look very dull and thin, but for other women with thick hair that gets huge, or straightish hair that just has a kink in it and doesn't lie well, then straightening can give a neat style that keeps in order all day and doesn't look a mess. If the choice is straighten or else be unable to maintain a style that is neither elbow length now ear length, then straightening makes sense. I'd say that there is a difference between this kind of grooming and thoughtlessly adhering to a particular style whether it suits one or not, which happens both with straighteners and with perms.