The audacity to even ask! I ain't even bothered by installing genuine versions of Windows anymore. All I'll ever run is AME Windows. It's basically Microsoft Windows but without Microsoft services. They recently changed a lot as they went from distributing ISO files to playbooks. You should definately check it out! https://ameliorated.io/
Right? I've loved ever since they starting debloating ISOs and currently am on their last released ISO. Now though, with playbooks, it's a bit more manual and also legal. Despite being in beta, it already looks and works quote well!
In mind of the developer it's about using your brain rather than relying on a anti-virus. Basically you don't want to download shady stuff or cracks with no verification or testing, and never open a pdf that came in the mail. But yeah, just me on my own I guess.
There was a time when I thought like you. I had no AV until Defender became a thing, and was fine. But these days I keep hearing about more and more exploits targeting your browser, or libraries in the OS that your image viewer might be using, etc etc.