Not all Chinese grow up speaking mandarin, however that is what they get taught in school. Students in Nigeria get taught standard English in school. Parents push for that knowing it can potentially improve their children's outlook.

We know whites who speak non standard English also suffer from job difficulties.

We know middle class immigrants like to get their kids to integrate into their new society by learning their new country's language and being proficient in it. We see this in France, Britain, Japan, etc. Fitting into the mainstream, like it or not, improves life opportunities. I know people like to retain their culture, and that's fine, but actively despising it and then saying the mainstream culture shuns you is unsurprising.

It's like bikers who dress like bikers do as to "enjoy" the the image that brings then complain they get reactions from people or police which affect them negatively, even if they aren't engaging in their aura. It's not exactly the same, but the mechanisms have similarity.