Because we are impacted. We are all now collectively learning what we can or cannot say and/or do.
It isn't fear of change. Many of us grew up in a time that was not kind at all to those who were different races, religions, or sexual orientation. We have grown a lot, and we continue to grow. Some of these changes are/were very necessary, and seeing that happen is wonderful.
Like I said before, I don't think anyone on here is purposefully trying to offend, including myself.
But it does impact all of us, because now we feel we have to scrutinize every word we say to anyone outside of our home.
I personally feel in our currently climate, I cannot be authentically myself in front of strangers because who knows what trigger word I could say innocently. I don't say offensive things, but then again, I never imagined saying "ladies and gentlemen" would be offensive.

I just didn't. Maybe I come from a different time than you. I am Gen X.
But basic phrases and actions I have used for almost a half of a century are all of a suddenly becoming offensive, and that is odd to me. And the rapid speed of everything single word being scrutinized is mind boggling. I truly think people are actively looking to be offended. To that end I ask, why? Looking to be offended is nonsense to me. And a huge waste of time.
Not all PC things are bad, please don't get me wrong.
But I just read an article recently that a professor claimed that Spongebob was a racist. HE IS A SPONGE! Omg, when does it end? It is this constant scrutiny over every detail that has impacted all of us.
I try to keep up because I do care enough not to offend someone, even though I may not understand it. But in that same token, I also have a right to think some things are hooey.
Either you can try to understand my side, or you won't.
However, I actively try to understand others. IMHO the best thing we can do as a society is look at both sides of the coin and work together.
So with that said, most of us to try and understand. However, we also feel inundated with the constant barrage of relearning how we are to be socially adapt in a world that is all of a sudden very different than what we used to know.