You should think of C as a front-end for the computing platform you are targeting. The platform has an ABI, which you need to use to interact with the system co

You should think of C as a front-end for the computing platform you are targeting. The platform has an ABI, which you need to use to interact with the system components. So because every third-party has to speak that ABI to interface with the platform, they might as well use that ABI to interface with each other too. You can of course build your own little world within a platform, with all your binaries speaking a different ABI to each other. And that might have some advantages, but most people find those advantages outweighed by just using the same ABI as the platform.