Sumana recommended a podcast episode on caffeine. It's a short episode, and it's good, and I recommend you listen to it. It focuses a lot on the "huh, it's weird that we've all agreed as a society that stimulant addiction in this one specific instance is okay!" of it all — which I don't mean in a dismissive way, just that I've encountered it a few times before and most recently in Michael Pollan's mediocre book on caffeine.
The thing that stuck with me the most about the episode was an amateur science experiment: a researcher ordered the same latte at the same coffee shop five or so times and discovered wildly different results. One day you might get 125mg of caffeine; the next, you might end up with double that amount.
This strikes me as deeply metaphorical for something — it's very easy, and very tempting, to mentally commoditize things that are in fact completely variable depending on a long tail of exogenous (or otherwise hidden) factors.