But they don't tho', that's why there's a problem. GPs hand out antibiotics like candy.
Vancomycin is the drug of choice for several major infections that are of a concern to hospitals (MRSA, C. difficile) because there's already pretty established resistance mechanisms. There are definitely some "more last ditch" drugs, but Vancomycin is kind of the first of the "Now we bring out the big guns" antibiotics.
Partially because it's a PITA to give to patients, and has some toxicity problems.