Primary care doc here. I agree that strep is "severe" as in "makes you uncomfortable with a fever, sore throat, enlarged tonsils, etc" but the infection generally resolves without antibiotics, if given proper time. The main rationale for treating strep pharyngitis (aside from appeasing patients) is prevention of rheumatic fever, a rare but devastating heart condition that occurs as a sequelae of untreated strep throat. Given the rareness of RF in the developed world, there are those in the infectious disease and primary care communities who think it is an excellent example of antibiotic overuse.