Why aren't residential areas built in the city center? What are the advantages of building between the business district and the industrial district?

I can only answer the first question of your question. Please judge the rest for yourself.

Xiamen Island Business Circle: From Siming Nanbei Road-Zhongshan Road Business Circle in the last century, it has developed into Zhongshan Road Area and Railway Station Area, and now it has several large areas such as Zhongshan Road Area, Bess-Hexiang West Road, Railway Station-Lianban -sm City Plaza along Jiahe Road Business Circle, Huli Park and Hong Wen Commercial Plaza.

Residential areas in Xiamen Island: Xiamen Port Area, Old Town, Hubin Yili to Liuli, Binglang New Village, Houyu Nanbeili, Lianyueli, Xiangeli, Lianbanxi Community, Yueyang Community, Lianhua Village 1 to 5, Punan New Village, Jinjiting, Qianpu Nanbei District, Jinshang Community, Le Kang New Village, Jiangtou Community, Jiangtou North District and Gao Lin Residential Area.

Industrial zones in Xiamen Island: Punan Industrial Zone, Lingdou Industrial Zone, Caitang Industrial Zone, Qianpu Industrial Zone, Software Park Phase II, Photoelectric Information Park, Houpu Industrial Zone, Xinhe Industrial Zone, Gao Lin Industrial Zone, Hecuo Industrial Zone, Heshan Industrial Zone and Huli Industrial Zone, mainly Huli District in Xiamen, in the east and north of the island.

Traffic conditions in Xiamen: People in Xiamen know about traffic jams, especially during rush hours, which are usually: Xianyue Road (the intersection of Culture and Art Center and Jinshang Road), Hubin South Road (Binnan Bus Station-Lianban Road), Hubin North Road (Du Dong-Lian Yue Road), Lvling Road (Lvcuo-Jinshang Road) and Xiahe Road (Lianban Road).