Comment Re:DNS Extension (Score 1) 187
(Disclaimer: I'm one of the authors of this I-D.)
Because by the time you went through all the steps you're describing here, you lost so much time already that the CDN may as well just serve you their content from the other side of the planet. CDNs are meant to *improve* latency. If two or more HTTP requests are needed to reach the goal, you really just completely miss it.
Also, HTTP caching wouldn't work very well if content gets served from "random" hostnames (because how else would you get the web browser to connect to the right CDN node?).
Remember that this is an EDNS0 option, to be implemented only by parties that need it. It's not intended to become a standard DNS feature.