The Arm 32 bit EABI spec acknowledgements section credits 9 other companies for their "active support" -- most of them are or were toolchain vendors. You specif

The Arm 32 bit EABI spec acknowledgements section credits 9 other companies for their "active support" -- most of them are or were toolchain vendors. You specify an ABI so that all the different companies who are writing and selling compilers can produce object files that work together, which makes it easier for customers to develop software for the CPU, which means you can sell more chips. Nobody will come and break down your door if you choose not to follow the ABI, of course, but if you want to interoperate with others you have that option. And yes, there's an implicit bias towards C and C++ here, but that is just because that is the environment where enough toolchain developers and customers care about interoperability between different suppliers to make specification worthwhile.