We used to use google.com for hosting jquery for us. Then when google.com started being blocked by the great firewall our site broke (it was pretty popular in China). It took a while to find out what went wrong, especially with the language barrier.
Back then we decided it's just better to self host. Less things can go wrong.
Unfortunately not. There is no benefit to leaving your critical files on anyone else’s infrastructure: https://csswizardry.com/2019/05/self-host-your-static-assets...