Zhuo surname is not a common surname in the history of China, and its number has always been relatively small. This may be related to the following factors:

1. surname change movement: during the Qing dynasty, there was a large-scale surname change movement. Many people changed their unlucky or unpleasant surnames and chose more common surnames, which may also lead to the decrease of some surnames, including Zhuo.

2. Social development and population migration: With the development of society and population migration, many surnames also show a decreasing trend. Some people with Zhuo surname may move to other places and merge with people with other surnames, making Zhuo surname rare in some areas.

3. Cultural tradition and family inheritance: The distribution of Zhuo surname may also be influenced by cultural tradition and family inheritance. In some areas, people prefer to inherit and use the surnames left by grandparents or fathers rather than create new surnames themselves. This may lead to a small distribution of Zhuo surnames in some areas.

Generally speaking, the reasons for the absence of Zhuo surname may be various, including historical, social, cultural and genetic factors. However, the population of Zhuo surname still maintains a certain distribution in the world and is relatively concentrated in some areas.