This was a calculated judgment call on their part not to offer a complete product to make their previous top-of-the-line product compatible with a new model. If you don't see the contradiction in those two statements then there is no need to continue. I don't come here to argue but to help, I can't help you with your angst at Canon.
Yes, I understand that the new strobe can be used with IR control. I understand that the same features of the 580EXII exist that existed before they released the 600.
I think it is quite normal for people with lots of pre-RT flashes to feel frustrated that those cannot work with Canon's RT system and they will have to keep using the third party RF triggers or optical triggers. It is a small frustration though, since they don't have to give up anything- only they can't take full advantage of the new tech. While this is similar on surface to the EF/FD debacle (cannot use the new AF technology/ newer bodies) it is a much smaller problem in magnitude. And less costly to boot.
On the other hand, Canon might have had a genuine problem in making the older speedlites RT-compatible (or not) and who knows, they just might release something in the future!
I am curious though, how does using a 600-RT setup improve on using, say, YN-622s with a 580EX II? I need to make that decision, so my curiosity is not merely academic.