Re: Why would people write in dialect anyway.
What is "writing" these days? For most people it is sending instant messages like Whatsapp or whatever or posting a few lines on social media.
Who is your audience? For many people it is others like them. My friends are mostly white and we "write" in messaging/social media in a pretty white way (but still some slang is used, I don't talk/write the same way I did when I was 18) Someone who is black and has mostly black friends is very likely to "write" in messaging/social media in a pretty black way using African American English.
That's different than a CV or "work report" and that can be a problem for black applicants who may have some of their dialect slip into those, giving those with an axe to grind a reason to bin the CV or give a poor evaluation for their ability to communicate at work even if their meaning was entirely clear.
If there's a work from home situation where nobody as met anyone or heard their voice, and they have pretty generic sounding names I think in the US someone writing with white southern dialect like "y'all" would meet with less bias than someone slipping in the occasional AAE colloquialism. Which shouldn't be the case, if someone wants to demand "standard English" they should look down on both equally. If they don't, they are biased.
Since instant messaging type services have become common in work environments, moreso with WFH arrangements, there's a lot of crossover. Are people supposed to use proper English in all IM communications with co-workers? So no emojis, no "k", no using "u" for "you" and so forth? If you think so fine, but I see that all the time, and use all those myself. I wouldn't put that stuff in a presentation that was going to be seen by the C level, but somewhere between IMs with co workers during the day and big time presentations there's a line where you should stop using dialect/colloquialisms. And I'm sure everyone has a different opinion of where that line is.