I'm sorry, but I can't outsource the computation of real time ultrasound denoising to EC2. Nor can I do the work of my LTE radio modem on EC2. Clouds and scaling out on clusters are great answer to a certain set of problems, but far from a panacea.
You certainly could pull off this architecture in a setting with a good LAN connection. Though I'm not really arguing that it's necessarily a great way to go.
It is entirely technical. Everyone who tried it shit all over it because it was a terrible experience, entirely due to limitations of internet connectivity (both latency and bandwidth).
The primary reasons these services didn't take off is that many users have shitty connections and almost everyone has a fast enough computer.