They’re using it for who knows how many dozens of things - simply a look at task manager on windows. They’re preloading heavens knows what to make the users experience better.

You’re talking about closed source operating systems and how they shouldn’t be using the ram that is available to them, and you think that I don’t have the faintest idea? 🤣

RAM is there to be used. You’re never using too much ram until you need to use more ram than you have. I’d have no issue with my windows using 60GB of RAM while “idling” if it makes the experience better, which it could.