And you're absolutely right about that - But it's a great OS for devices that you don't own. Leaving aside the (frequent, ugly, and probably illegal) times that school districts require parents to purchase children chromeOS devices that get joined to the school's domain, it's a very common problem to want to have devices that are locked down according to organization policy. When you are giving a device you own to someone else to physically control, the ChromeOS Straight Jacket is a great tool.

There's a distinct problem with it being the only tool around, though.