> Why do programmers always need a library between them and the API?

You do know that libraries present an API, right? Very few people program on Linux or other OSes without using libc or the OS/distribution equivalent, and for good reason. Those libraries provide a degree of compatibility across hardware systems and operating systems (and even the same OS but different versions).

Your question is about as sensible as asking "Why do programmers always need a programming language between them and the machine code?" Because it improves portability, reusability, reasonability, and on and on. Though, since you hate abstractions, maybe you do only program in machine code.