Well, it is only 0.00000000000000000000000000000000000000000000000000000014% of all possible SHA26 hashes (assuming a bijective mapping, so probably a bit higher, if there are collisions).
True, but in the context of a brainwallet where even a big 8 character passphrase consisting of random alphanumerical characters (eg.
_Cf}u$b0) needs computing 6 quadrillion hashes (0.006 quintillion) in total, the "165 quintillion hashes per second" rate is huge.