until it is widely used and supported, there is a big cost to adding features to a CDN. the means dont justify the ends.
And how is it supposed to be used if CDNs don't support it? Sounds like a circular dependency to me. Technology is here, but without infrastructure it's close to impossible to use at scale.
You cut flash out and then the need to support it pops up.
Catch 22. To cut Flash out you need to use DASH + MSE. You come to CDN and say you need it, and they say they don't support it because you first need to use it...
Google worked around it by rolling out their own CDN. Do you propose to do the same?