How come doctors are reluctant to prescribe amphetamines and benzos?

Do No Harm. A major principle of medicine is to do no harm if it can be avoided. There are a lot of alternative better medicines than benzo's and amphetamines. Doctors who do not pay attention to the harm these can do to their patients can lose their licenses, their freedom, and livelihood. With the cost of a medical education today running about 250K, it is not worth it to use such problem meds.
Potential problems. Prescription medications are now the fastest growing drugs of abuse. There is a lot of diversion of these meds as there is a street value. In high schools and colleges increasing amounts are misused and abused to such an extent they now serve as currency. Benzos and amphetamines can cause addiction, serious side effects and benzos addiction can be difficult to treat.