The goal is banishing any and all questions of what to download, what desktop, what apps, packaging formats, software stores, user accounts, backing up, all of it: run the browser locally, sync the data – and only the data – to the cloud. That is not really popular in the open source world. Who finances the cloud, is it open, who can read or sell your data?
ChromeOS is a product designed to suck people further in to the Google ecosystem. All its limitations, like basically being a web browser with access to the Android Play store, are built around that. The simplicity of not having to worry about anything else is how Google sells that as a benefit of their platform to the masses.
I don't know any of my fellow nerds who want a ChromeOS kind of experience, so why would any of us dedicate our free time to making one?