Windows

Multimedia and gaming. Almost everything runs out of the box within a minute. I often get the same results with Linux, but sometimes it takes more work and I don't always have the time or the muse to put in the effort.

Some proprietary software only runs on Windows. Famous examples are Adobe products. There are Linux alternatives, but that's not always an option in a corporate environment.

This is important to me: Windows generally has fewer barriers for beginners (with whom I often work). While I've introduced a number of people to Linux and seen success, it's just not as easy. It may also be a matter of what people already know, which is Windows (and increasingly Android or iOS).

In my experience, updates break Windows less than Linux, but that may just be me.

Device compatibility/driver support is also better (some printers or wireless network adapters, for example). Linux is catching up, which is fantastic. But it's still catching up.

Linux

Programming, servers and everything security related, which is huge! I don't think we need to go into that. In line with that: I hate Microsoft's data collection practices. Some distros collect too, but it pales in comparison to Windows.

It is free. That's a big deal for some people, especially in poorer areas. Windows can't compete with that. It is also a great option for companies that want to save a bit of money and go open source, although the wisdom of that is debatable in some cases.

Not so important to me, but some love that it's a fantastically customisable system, an enthusiast's dream.

I could go on. Feel free to disagree or agree with what I've said. I am curious to hear where you think I am wrong, right or simply have a preference.