LifeOmic - the company I work for - has a high focus on wellness and health science, with all of our apps having scientific backing. I brought up that hydration would make a good additional wellness "pillar" to our existing 5 of Vegetables, Mindfulness, Physical Activity, Sleep, and Fasting. It started an interesting discussion that apparently the science behind hydration has been really bad and that there's no good way to track how much water people need to drink, because water needs vary so widely based on geography, activity, job, body type, metabolism, and even foods eaten. This means that the traditional "8 glasses of water per day" thing is a total myth.
After reading this and a lot of the articles linked from it, I'm convinced about the myth, though I do have one thought not mentioned in them - I think that putting a focus on drinking water specifically can lead to a *reduction* in consumption of *bad* things like sugary drinks, or too much caffeine.