Switching to another LLM isn't always about quality. Being able to host something yourself at a lower or equal quality might be preferred due to cost or other reasons; in this case, there's no assumption that the "new" model will have comparable outputs to another LLM's specific prompt style.

In a lot of cases, you can swap models easier but all the prompt tweaking you did originally will probably need to be done again with the new model's black box.