The thing is, the Settings an on iOS contains both system and app settings (unless an app decides to have its settings within the app, which some do, but even then stuff like notification settings for that app or which data it is allowed to access will still be found in the Settings app). So it makes sense to call it just "Settings" on iOS since that's where you usually have to go to change any settings.
On the Mac, the System Preferences app only really contains settings for the system itself, and the settings for each app will be found in that individual app for the most part. So I'd argue it would actually create confusion if the System Preferences app was renamed to just "Settings" like it's iOS-counterpart because people would click on the app icon expecting to find the settings there of any app.
If you are using an app and you see the little gear icon in the dock along with the name "Settings", then that's what opens the settings for your current app, right? That logic would make sense to a lot of people, but instead they would just end up in the completely unrelated settings panel for the system as a whole, with no panel for an app you're currently in. The name "System preferences" on the other end is indicative of the fact that this is not where you find the app settings in and that you have to look for them in the app itself.
