One factor is that "Adrenaclick" is not a generic EpiPen. It is a different branded epinephrine autoinjector, with generic versions available. The FDA regulates epinephrine autoinjectors so that a prescription for EpiPen must be filled with an injector that has the same operating instructions as EpiPen. Adrenaclick and generics do not have the same operating instructions as EpiPen.

It's not a completely ridiculous regulatory decision, but it certainly factors into people not using the alternatives.