The reason why Qin Shihuang ordered Xiao Zhuan to be the written language used by officials and people all over the country is because the six countries are unified, and it is very inconvenient to communicate with each other in their own language. The purpose of unifying words is to facilitate communication. At the same time, he did not order the abolition of other characters, nor did he stipulate what penalties would be imposed if other characters were used instead of Xiao Zhuan, nor did he set up corresponding institutions to supervise and manage them. Therefore, officials and people in the Qin Dynasty can still use other languages, but seal characters should be used in some official documents, memorials, good news and notices.
But even if the officials and people of the Qin Dynasty were able to use other languages, why were there so many official scripts? Why can't it be Xiao Zhuan or other characters? In other words, why did officials and people choose to write official script? Then it depends on the characteristics of official script compared with other characters, which is worthy of the choice of officials and people.
Compared with other languages, the biggest feature of official script is that it is easy to write and can be written quickly. Just like today, people use the same language, but most people will choose to write running script or running script, because both running script and running script have Lian Bi, which can be written quickly. In some occasions, such as meetings, it is necessary for us to take notes quickly in class. The people and officials in Qin dynasty also needed a kind of writing that could be written quickly on some occasions, and official script could meet this demand.
Therefore, compared with other characters, official script should be used by more people, and most of the characters on the cultural relics unearthed in Qin Dynasty are official scripts.