CDN doesn't help at all, if it is based on caching only (like CloudFlare). In some cases http headers prevent all benefits of having cdn. Like pages with no-store, no-cache, post&precheck=0. In these cases CDN might only add latency.
I have seen sites hosting images with those headers too. (like Google sites). If you're using slower network connection it becames painfully apparent that all images are always completely redownloaded. With these parameters images must be downloaded from the source, or otherwise caching cdn would break things. Other cdn networks like coral cache clearly states that they always cache content, what ever headers say... But it isn't acceptable for all sites.
I have seen sites hosting images with those headers too. (like Google sites). If you're using slower network connection it becames painfully apparent that all images are always completely redownloaded. With these parameters images must be downloaded from the source, or otherwise caching cdn would break things. Other cdn networks like coral cache clearly states that they always cache content, what ever headers say... But it isn't acceptable for all sites.