Cryptocurrency mining ASICs cannot be used for password cracking because they are not designed to hash arbitrary strings, and do not support arbitrary scrypt parameterization. They are designed to take in a block template of some sort, and then internally handle iterating the nonce to minimize load on the communication bus and the host processor.

An interesting thing about GPU password cracking that many people don't realize is that the GPU is responsible for not only hashing candidate passwords, but also generating those candidate passwords. The bus bandwidth isn't enough and the CPU isn't fast enough to keep it fed with candidate passwords otherwise.

You could, of course, build password cracking ASICs that have internal processors for generating candidate passwords, but I'm not convinced that it doesn't make more sense to stick with GPUs or maybe FPGAs there.