Well, in the case of Linux, also free. Many years ago I built an HTPC to run a media center at home and I got it all done and I realized that I didn't actually HAVE install media (or a spare license) for windows and it kinda irritated me that a legitimate license was going to cost me like $100 for a computer that wouldn't ever do anything but stream media from my own server. I had heard of linux before and I really wanted to make sure that my hardware worked without having to figure out how to actually buy windows and wound up installing ubuntu to test it out. I was surprised to discover that once installed it wasn't really all that different from Windows and decided then and there that this would be perfectly adequate for my HTPC and wound up using linux on various machines ever since. (I always have an old thinkpad running some flavor of linux for most of my general computing).

Like a lot of folks, I think the only thing I use windows for is working remotely and gaming (although, that is less and less the case since I got a steam deck and linux support for gaming has gotten SO much better over the last ten years).