Sichuanese: It's because a group of people came during the crackdown in the 1980s and gradually accumulated, so it's natural for relatives to bring friends.

Hubei people: It originated in the 1990s when the state smashed the iron rice bowl and disintegrated some large state-owned garment factories in Wuhan. Many employees went south to Guangdong to make clothes, and gradually more relatives and friends brought them.

I come from Jiangxi and make clothes in Guangzhou, so that's all I know. This is hearsay.