I think every major OS ships with some sort of calculator. The problem is discoverability. If you're in the middle of browsing, it's quite a bit of effort to say "oh that's right I have a calculator on here let me just find it in the start menu/Applications folder" as opposed to it
just being there in the same app you're already using.
Widgets would be a potential solution but they keep being tried and abandoned soon after in desktop OSes.