Likely the biggest advantage of antibiotics, in terms of their use to treat disease, is that they can help the body fight off infections or other bacterial issues that the body will struggle to deal with on its own. They can be administered in a variety of ways, orally, intravenously as well as topically with the use of creams or even eye drops. They are relatively inexpensive to produce and come in natural, semi synthetic and synthetic varieties, and many of them have different uses depending on their strength and makeup.
There are a huge variety of antibiotics as medical science now has to search for new ways to use them in order to combat some of the new resistant strains of various bacteria. They still have an enormously wide application.