Renting software that runs from the cloud is one thing (and Creative Cloud doesn't really run from the cloud; most of the actual software is on your computer, but it updates from the cloud and requires an active subscription in order to run). Running an operating system from the cloud is another thing.
Can it be done? Sure. Apple allows you to boot a computer from a copy of OS X living on a NetBoot server.
Do you want to do it? Except in certain very limited circumstances, no. Even if you have a very fast local area network, it's going to be agonizingly slow compared even to a slow hard drive, much less to a SSD. Everyone wants fast computers, not slower.
Running an OS from the cloud creates huge demands on bandwidth, a miserable user experience, and any network interruption crashes your computer. It's hard to see a business model for this. Apple is a hardware company, not a software company; they want to ship boxes, not OS licenses. And they don't want to pay for the bandwidth to run an operating system from their servers, or deal with the complaints about what a terrible experience it is.
Chrome OS, Google's cloud-based operating system, is only intended for doing simple online tasks (using Google's services, natch) and isn't intended as a desktop operating system...and even it only has niche markets, really.
