Largely we don’t address the long hair issues because the solution is pretty straight forward (as shown by the-hero-dies aka Kevin Warren):
As for the okay/appropriateness – it generally depends on the consistency and suspension of disbelief. It’s common practice in all kinds of media to have named characters go without helmets do they can be easily recognized and in more than a few productions the men have equally impractical hair styles.
When it becomes a problem is when products signal that some men are practical and/or warriors by giving them close cropped hair styles and then give women with equal responsibility fancy hair styles because they have an arbitrary checklist of traits all women need. Such as:
Then it’s terrible because it showcases the double standard, objectifies women and destroys the visual story telling by mixing the messages on what a character’s appearance is supposed to tell us.
– wincenworks