Doctors are pre-disposed to do something rather than nothing, and doing something is more dangerous than doing nothing in the vast majority of medical cases. This is especially true when "doing something" has unknown or unbounded side effects and the original ailment is something that the body will take care of by itself in short order.
Every prescription you take for a minor inconvenience is a tiny chance that you're taking the next recalled drug for something that does long-term damage that wasn't found in short-term medical trials, or the chance that your pharmacist makes an error in filling the prescription.