It's a means to promote and enforce social protections and decency. But it's been hijacked to an extent and I blame social media for it. It's given a platform for loud people who think they mean well to instantaneously tear others down en masse. They're overtly sensitive, biased and intolerant in their beliefs but can easily wrap their outrage in the guise of morality so that if anyone dare go against it it must mean they're morally corrupt in some way.
Whereas in the past u might have had the odd sensitive person bother to make the effort to call in or write letters of complaint on an individual basis, everyone's now got a phone with instant, easy access to social media where all it takes is a dead simple retweet to send bad takes around the world like wildfire. This is especially troublesome when apps like Twitter force the discussion of complex issues into bite sized text limitations. Everyone's ADHD now, stuck in algorithmic echo chambers providing us with everything we want to hear and nothing we don't.
Social media's allowed this collective outrage to be put on blast. It's placed a negative pressure on companies, organizations, networks, etc to fall in line with these calls for sensitivity, lest they appear insensitive and suffer public condemnation for it. These entities are naturally risk averse so they'll lap it all up if it means their image and profit margins remain in safe territory.
It's still doing its sensible job of keeping blatantly disrespectful and offensive shit at bay. But it's definitely become performative at its most absurd, and it's the absurdities, like the cancelling/ostracizing without due process, that make the headlines and gather the most pushback. Rightists also somewhat blow the problem out of proportion and it often seems like their only motive in decrying PCness is to conveniently excuse their own offensiveness and bigotry.