baffling medical mysteries ( not really its all a conspiracy right chyyeeeahhh )

Few reasons imo

colds germs mutate at a fast rate that's why our natural immunity fails most of the time
antibiotics r indicated on a gram stain + or - basis n they have cell walls that r hard to break thru n make the infected cells

over prescription of antibiotics causes 2 things the host to become immune to the antibiotics and the germ to recognize the antibiotics and thereby render in ineffective
The more a germ recognizes the antibiotic and renders it ineffective the less medication we have to battle it and then it creates 'superbugs' which medicine can't treat

Ita more a cost benefit analysis then anything they don't want to prescribe bc although surface receptors differ on cold types basic genetic makeup is fairly similar and the more drugs u introduce to cure the infection the less future defense the patient has to prospective colds

so destro is right a cold won't kill u so they treat it n save the stronger drugs for wen they r truely needed