Seems like I somewhat underestimated the hairpins, but on the other hand, I think it's also quite ceremonial, in the end, since it's kind of doubful the emperor's harem would be a free for all place, even if it's just a maid. The truth is the emperor could, at any time, lock his eyes on any of them women there to take them and promote if he wanted to. If those women were "sullied" by outsiders already, it would be kind of strange. Thus I think the women simply make a big deal out of it since their lives in the harem grounds are kind of empty and boring, mostly. Of course if a woman leaves the harem, it's a different thing, but I already covered that in my earlier comment, so that part wasn't an underestimation.