Well, sure, but the patient doesn't write the script so they're not the one with the power, and if it was 'medically approved' to tell patients how to change their diet, what types of exercise would help, then the patient would simply waste their time going from doctor to doctor getting the same response. Thus the medical community is complicit in taking 'the easy way' in this instance. I'm not a fan of for-profit medicine, which could be somewhat responsible for the patient entitlement complex fueled by commercials which say 'Ask your doctor' but probably mean more along the lines of 'tell your doctor to give it to you' in practical terms.