I always thought the confounding factor was that coffee keeps you productive. Meaning, drinking coffee gives you (superior) employment, which means you get decent health care. You also might gain some meaning in life from your job. You will also probably get some extra human interaction with coworkers as well.

Going to work and being a part of a large organization that works on cool products definitely “energizes” me. I have friends at work that I enjoy seeing daily. I would have a hard time keeping my job without caffeine. I could easily see all the ancillary life benefits of being caffeine addicted being the primary reason why coffee seems to be good for health in all these studies.