It makes it possible to change the API of system calls or completely remove them if better ideas come along for implementing their functionality. Without it, y

It makes it possible to change the API of system calls or completely remove them if better ideas come along for implementing their functionality. Without it, you end up maintaining system calls that nobody should use. Now, you could argue that moves the mess to the c library, which would still have deprecated functions that used to call old system calls, but now are built on top of better ones, but there’s more flexibility there. Application programmers can, one by one, move to newer c libraries that remove that cruft.