More unlikely is not 0, and you don't want to skip all the mid points and create the super bug in one treatment. Probably safe if you do this now and then, but

More unlikely is not 0, and you don't want to skip all the mid points and create the super bug in one treatment. Probably safe if you do this now and then, but not if it's the SOP for antibiotics. No idea if that's why they don't do it. Side effects sounds plausible too. Also, remember that medicine is all about postponing the inevitable. We put a ton of money into postponing a person's death. It makes sense that, if they don't have a better alternative, they would continue to use these antibiotics if they got local results even if the practice has an expiration date.