Gotcha. I guess it's an OS expectation thing then. In OS-X, it's pretty much an assumption that dynamic linking is what's going to happen (good or bad).
Linux userland has various libcs available (klibc, glibc, eglibc, uclibc, dietlibc, musl, …), with distributions occasionally switching between them, and ABI-incompatible changes happen every once in a while. Source-distributed software does not have to care usually, but for binary-only distribution, statically compiling the libc is the easiest bet. Thus, the kernel has to maintain compatibility.
More than that, static linking is very difficult indeed as there is not even a crt for static linking let alone libc.a, you would have to write your own.
Thanks for clarifying this point for me.