Before their blacklisting in the 1970's CSA (after which amp use dropped by 80-90%), amphetamines were recognized as awesome pills. In the casual/new user, 5-15mg of dextroamphetamine, banishes fatigue and lifts the spirits of the depressed, of course methamp is even stronger and longer lasting.
After benzedrines introduction to medicine in the late 30's, amphets were sold by Docs script and in OTC form until the 1970 CSA put a fear into Docs who scripted pep pills, dexies, bennies, goofballs (ampht+barb combos).
Instead of the 'speed kills' mantra, amphetamines were praised for their safety and long list of medical problems they could treat. Epilepsy, head injury, Parkinsons, hyperkinesia, asthma, nasal stuffiness, barbiturate and opiate poisoning, narcolepsy, alcoholism, obesity. Meth was used with success in helping people withdraw form opiate addiction.
Finally after their continueing misuse/abuse after the 1950s, in 1965, the drug abuse amendment act classed amphetamines, barbiturates, and similar medical wonders as 'dangerous drugs' leading to the CSA in 1970 of scheduling we have today.