The reason used to be performance, but now with modern browsers and especially HTTP3 I doubt that is true anymore. I guess the separation into CDN and non-CDN

The reason used to be performance, but now with modern browsers and especially HTTP3 I doubt that is true anymore. I guess the separation into CDN and non-CDN stuff could still make sense since you can serve static resources from even closer to the user than you serve your dynamic stuff while avoiding having the CDN proxy traffic to the website backend.