The opacity of the application/acceptance process is largely to blame, imho, for some of the freakout over grades. Note that this is mainly limited to the higher end kids because they’re trying to get into ultra-selective schools. Kids read hard statistics on the admitted/enrolled students at those schools and see things like, “Over 95% of our students are in the top 10% of their HS class”. Boom! The grade freakouts and HS AP arms race are a natural result. Same goes for the SAT & ACT arms race. Those are the only facts that are visible in the selection results and, importantly, the only real things the kids can control.
It doesn’t help that kids don’t get any feedback on their application other than a yes, no, or wait (deferred). Why did my D18 and all her friends (and everyone they know) get flat out rejected by Stanford REA? No one knows! What are the juniors at her HS supposed to do in response to those results? An obvious one would be, “I need to take more AP classes to stand out to the AOs”.