Even a recent book advocating the efficacy of prayer in treating disease (Larry Dossey, Healing Words) is troubled by the fact that some diseases are more easily cured or mitigated than others. If prayer works, why can’t God cure cancer or grow back a severed limb?

– Carl Sagan, The Demon Haunted World (1995)

See also https://www.whywontgodhealamputees.com/