Is there any actual medical use for amphetamines?

Yes: The main one is attention deficit hyperactivity disorder, in which d-amphetamine or a combination of d- and l-amphetamines are the drugs of choice in this condition. The doses used are much lower than the doses of abuse, and in adhd there is seldom the tolerance, craving or withdrawal symptoms of addiction. They are also used for narcolepsy and as adjuncts in treatment-resistant depression.

Yes!: Methamphetamine has no or very narrow medical uses. But Dextroamphetamine is remarkably safe & extremely useful in treating adhd, narcolepsy, excessive daytime somnolence, shift work dyssomnia, obesity, and as an adjunct to cancer treatment or for depression (in low doses).