The human body has a built-in mechanism for fighting off disease and infection known as the innate immune system. When the epidermis is compromised through insult or injury, the innate immune system kicks in gear, more specifically Cathelicidins who direct the innate immune system to first to kill any pathogens, then clean the compromised tissue, then repair it.
Antibiotics changed all of that. When Alexander Fleming discovered penicillin, introducing the antibiotic age, bacterial infection, strep throat, recovery from surgery, soon became minor considerations For decades, quality of life extended, life expectancy grew, and we as a society grew accustomed to the miracle of antibiotics. Antibiotics would wipe out the bacteria colonies allowing the innate immune system to fulfill its normal function of killing, cleaning, and repairing the body.