Nobody cares. Hashes are plenty fast. Even the code complexity doesn't matter: I've implemented both SHA-256, and SHA-512, take less than a hundred lines of code. And of course, Linus would have use some existing implementation.

Also, "more secure" doesn't necessarily mean "more complex", or "slower". Blake2b for instance is as fast as md5 and has a simple RAX (xor, rot, add) core from Chacha20.