It is a mistake to believe caffeine is not a drug. It produces all the symptoms that make it one: addiction, withdrawal without it, decreased effectiveness with increased tolerance, makes the user irritated without it, etc.
Society has made this drug accepted and others not. It changes the neural activity in your brain. It even changes the structure by creating new receptors with long term use…opioids do this too. The drug’s acceptability is a construct even more pervasive than is the attitude toward alcohol. We are expected to use before work! At work! On lunch! During breaks! We view non-addicts as anomalies or “health nuts.” Strange that we view non-drug use as a form of extremism.