To the best of my current understanding, (microscopic) reversibility is crucial to get something which looks like classical thermodynamics—i.e. second law, thermal efficiency limit, etc. Without reversibility, we could still apply similar reasoning and get analogous results, but there would be extra steps and the end result would look qualitatively different. Roughly speaking, we’d need to separate out the steps which reduce the number of microstates from the steps which move around our uncertainty about the microstate.
So, the assumption here is in service of reproducing classical thermodynamics, which is in turn a way to test that I’m setting things up right before moving on to more general applications.
To the best of my current understanding, (microscopic) reversibility is crucial to get something which looks like classical thermodynamics—i.e. second law, thermal efficiency limit, etc. Without reversibility, we could still apply similar reasoning and get analogous results, but there would be extra steps and the end result would look qualitatively different. Roughly speaking, we’d need to separate out the steps which reduce the number of microstates from the steps which move around our uncertainty about the microstate.
So, the assumption here is in service of reproducing classical thermodynamics, which is in turn a way to test that I’m setting things up right before moving on to more general applications.