There is no known proof that one way functions exist. But what is the heuristic evidence that they exist?
I sometimes read that the existence of cryptography is heuristic evidence that they exist. E.g. the ciphertext from a block cipher like AES is easily computable if you know the plaintext and key, but the key is not easily computable if you know the plaintext and ciphertext.
This is seen as evidence that AES might be a one way function, but to me it simply suggests that we don't know how to invert AES. In other words, it seems like this is an algorithm-search problem that is very hard (finding the key inversion algorithm), not that that algorithm doesn't exist.
Is my reasoning correct? Whether it is or not, what is the heuristic evidence that one way functions exist?