ChromeOS has a very specific use-case: a basic machine for non-techies who only need a browser. For example, your mum who just wants to read some emails, look at some photos, or do some shopping.

Yes it's way less usable, but that's kind of a plus in this case because you're getting a simple machine which is hard to break, and Google is doing the tech support rather than you.

I've got no desire to use it myself, but I'd rather an elderly family member get a cheap Chromebook than keep using an unpatched and insecure old version of Windows or pay through the nose for a Mac they don't need.