At my dojo in Japan only the yudansha and sensei wore Hakama. However, when teaching the children's classes, if a kyu level adult was acting as an assistant teacher that day, Sensei would have them put on hakama. (but kids classes are different: they gave them colored belts too, to motivate them).
One of the most embarassing days for me was when as a 5-kyu I somehow showed up with my gi, but no belt. Our Sensei was out and the class was being handled by one of the higher ranking students (3 or 4 dan?) and his solution was "no problem, here, just use this belt," and handed me an extra black belt that belonged to our Sensei! I protested but he insisted that it was no big deal and was certainly preferable to me sitting out the class. So I put it on, much to the amusement of the other kyus in attendance. Things only got more embarassing when Sensei arrived later and joked that I must have learned a lot in the first half of that day's class to make it to shodan already, ha!