Having seen too many "this randomness function was never meant to be used for security, but people use it for security anyway" vulnerabilities in the past:
Can we PLEASEPLEASEPLEASE have this secure by default from the beginning?
Can we PLEASEPLEASEPLEASE have this secure by default from the beginning?
I would bet someone is already working on it as we speak.
Introducing cryptography in the STANDARD for stylesheets adds complexity where it doesn't belong. Ultimately a browser vendor isn't responsible when a company sells insecure cryptography.
Adding crypto to CSS will bring us nearer to bitcoin mining in the CSS engine.