Exactly The most common cause of acne is generally accepted to be hormones, however it begs the question. If hormones are the direct cause of the acne then why does he need an Anti-Biotic.
If lets say that hormones are simply the precursor to acne by inducing heavier(simple terms) sweat and once that sweat stagnates on your face bacteria goes and live in the sweat multiply and so on. and the acne is actually bacteria festering the skin(in a sense a bacteria infection), the idea here is to kill the bacteria but why not instead simply wash your face?
Much like a persons armpit, The sweat does not make the foul oder its the bacteria that invades the area to live and breed in the sweat. and a doctors solution is to kill the bacteria but in truth one can simply avoid it by washing.
Same rule applys to why some people generally gain acne around the mouth area, thats where you insert food and oil from the food builds up around this area. And again bacteria invades the area. Washing ones face with the popper solution after eating can help fix the problem.
The reason i suggest to keep your hands off your face is because you transmit bacteria from your hands to your face. ( another good reason to wash your hands before eating.)
However some people simply have a genetic predisposition to acne where no matter how much one cleans you will have acne to some degree. and these are the types of people where medication and or other treatments might be helpful.