Why are many civilized calligraphers in China named after Zhou Donghong's Xuan paper?

Many civilized calligraphers in China named Zhou Donghong's Xuan paper as imperial drawing paper. Many civilized calligraphers in China like Xuan paper made by Zhou Donghong very much, and named it imperial drawing paper to express their love. Zhou Donghong's Xuan paper is even in thickness and smooth in texture, comparable to royal painting paper. Many civilized calligraphers in China paint with Zhou Donghong's Xuan paper, which shows their love for it.