Drugs are a sensible option for those who cannot achieve a high degree of pleasure through sexual experience. All our states of happiness, and all success in pursuing pleasure, are ultimately derived from brain chemistry.
Drugs are valuable tools to induce states of happiness when we cannot experience them sexually.
Even hard drugs, primarily those derived from opium, may be a sensible choice when we suffer from a terminal disease, or when, for whatever reason, we cannot expect to get back on track in life.