Most common maybe. I feel most windows users aren’t actively choosing to use windows. It’s just what they are left with.
People usually choose to use Linux or Mac. As Linux is rarely preinstalled or like Mac more expensive (when it comes preinstalled) than the windows devices for sale. I’m not convinced given a fair shake, windows would have the market share it does.
Servers have highly informed people making decisions about their operating systems. When weighing the options about uptime, security, etc they rarely choose windows. Cost isn’t really a factor relative to the price and operation of the server.
Plus they can validate the data they harvest when you pay. They’ve got transactions and identity information once you pay.