I would argue those of us on a shifted circadian rhythm that lags 4 hours behind the farmer personalities in our society need caffeine to fit into the rigid corporate structure those first hours of the work day, and those high pressure professionals, VCs, high tech biotech silicon valley wall street types need caffeine (and cocaine for some lol) to function in their 17h 6-7 day work weeks (not me). I just take a caffeine break on vacations to reset my sensitivity and then slowly build up over the next 6 months to a pot of coffee all the way through before bed time to function.