My husband stopped getting haircuts and shaving awhile ago, and to keep his hair out of his face when he's working he'll just tie it back at the nape of his neck (not really on the top of his head). At home or out and about, it just hangs free.
I don't think he really does it to be cool, he just told me he got tired of all the clipping and shaving, and what not. And that when he was on the ranch in MT, he didn't really maintain it either, and he feels much more comfortable this way. But his hair is naturally curvy and wavy, so it looks nice when it hangs free. He's also got a pretty strong beard going that he trims every once in awhile.
It's just hair. I don't have a problem with it (I actually think it's pretty handsome on him), and even if I did have a problem with it- what would he care? It's his head. Not going to nag him about it and act self-righteous about a ponytail. You want to wear a ponytail - just do it. (But for the love of geebus, keep your hair clean!!!)