Why did the Eight Banners of Manchuria not shave their hair and change their uniforms to the Eight-Power Allied Forces?

It's very simple, because they can't defeat the Eight-Nation Alliance, so of course they can't shave their hair and change their clothes. As early as the Kangxi era, the only way to attack Taiwan was to rely on green troops. During the Qianlong era, the so-called Eight Banners of Manchuria were mounted on horseback, with men falling from their saddles and shooting arrows. Even if the Eight-Nation Allied Forces did not have powerful firearms, the Eight Banners masters might not be the opponents of foreigners.