In fact, there are quite a lot of races in Hong Kong, but why don't there even be ethnic names or autonomous counties like the mainland?

First of all, it has a lot to do with area. It is necessary to know how big the whole area of Hong Kong is and how many people can race under such an area, so if you set up an autonomous county or something, it is possible that you will cross the county by buying something, which is very chaotic and not conducive to management. In this case, it is better to set up an autonomous county than not to set up an autonomous county.