Chrome OS isn't really a desktop OS either. Chrome OS is the current incarnation of the dumb terminal (I know that there is local processing but the purpose is locking you up to Googles servers and services). Chrome OS is a tool for locking your data in with Google. That is even worse than MS locking in your desktop - at least you control your data there. In Chrome OS you control neither. They have to pay ME for get me to use one.
I've been in the computer field for more decades than I care to remember, and I couldn't count the number of times I've seen people lose priceless data (because it happens so often).
They get viruses that eat their data; they don't backup their data; they backup their data incorrectly; their data and backup gets destroyed (e.g., house fires); etc.
For average people, having a company like Google hold onto your data is a good idea. Google will do a much better job keeping it safe than your average person.
Also, Google does a great job making it easy to make a local copy of all your stuff stored on Google (email, docs, spreadsheets, etc.) so I don't think your lock in comment is entirely fair.
Not to mention the care and feeding Windows requires, it's insane. It's ridiculously easy to get viruses and malware, it's ridiculously easy for your system to start running unbearably slow. It's because Windows is far too hard for average people to understand and administer properly. And it's not the average person's fault, they shouldn't have to be computer geniuses to use a computer.
Chromebooks are an absolutely fantastic solution for lots of people.