Because none of that stuff existed in the '50s, '60s, and '70s? /s
Just substitute "nuclear war for "climate change".
My wife and I cannot talk about climate change around our kids because they understand how scary it is and we see their fear about the consequences.
Ideally, kids would develop, by trial and error, effective strategies for identifying solvable problems and dealing with them, and not being extremely negatively affected by (directly) unsolvable problems. It would be beneficial for society if people heard about climate change and thought, "Okay, that won't be good, so what are some things I can do in the short term and in the long term to make a positive impact?" The great thing about such an approach is that it's omni-applicable, such as when one's car breaks down on a long drive, etc.
Parents who constantly hover around their kids presumably interfere with this vital process, perhaps because these important lessons can only be discovered, not forcibly taught.
There is no rational evaluation of real dangers and this irrationality is one, if not the most prominent, driving factors for policy. Hell, people are scared because of tweets and mass surveillance is implemented with justifications an occult voodoo mom would get a red face for.
What do you expect to get from police checks in front of schools? And people wonder about school shooters? Seriously?
It doesn't sound like you interact with many "kids" these days. As someone surrounded mostly by them, I can assure you none of this is true. Sad to see this upvoted so highly and especially sad to see people pointing out this is a long brought up conservative talking point with no evidence downvoted. I thought we got over this myth 10 years ago. Yet people still want to yell at Mr. Rodgers for caring about child psychology and being on the forefront of mental health in a real way...
Perhaps one should look to the external world these people are coming into for answers. Climate change, the economy, and the political climate with hateful policies against many people over the world in many countries.
Not to mention that mental health being destigmatized raises statistical reporting rates as people are simply more open about it.
But yeah, let's blame bad parenting that people first accused millennials of when no millennials are even left in the post high school college population.