Removing antibiotics as a cheap default option (as it is in the US) creates an economic incentive to ensure livestock health and welfare. In practice antibiotics are used mostly to compensate for unhealthy conditions and to increase yield (i think only by about %10 for milk, for instance). Keeping livestock on broad spectrum antibiotics continuously for their entire lives is not only medically unnecessary, but deeply irresponsible and a contributor to rising antibiotic resistance.