Breathing muscles are the same as any other muscle. If you don't use them, you lose them. They will always function, but not to the same extent as they could if you use them properly. They will keep you alive but not help you thrive.
Correct breathing is what we do naturally, but we lose that and we don't notice it, and it messes up everything. If you can get back to good and naturally effective breathing, you can improve your health without medication.