I wouldn’t hesitate to wear pads to an XC race and have many times. I race expert womens but started wearing pads for ALL MTB RIDES (including races) after a crash on an easy trail I was extremely familiar with nearly gave me an injury as bad as Chloe Dygert’s. Thankfully didn’t sever my muscle tissue but >$1,000 ER bill and weeks off the bike isn’t worth it. I swore to myself I’d never MTB without knee pads again and over two years later I’ve kept that promise. Anyone who gives anyone else sh*t for wearing pads/full face helmet/etc can go back to elementary school.
I think crashing is more common during racing because of the adrenaline, higher heart rate, and higher pace than you’re used to.