In healthy people with no underlying conditions the need to be constantly "hydrated" is overhyped.
I've got a pair of 300ml bottles for my running belt for long runs. If I drink well in the hours building up to a run, I can get back with plenty of spare fluid after a couple of hours running. In the majority of circumstances, I don't need water on a run that is an hour or less. Most of the time, I get back and am still well hydrated with light coloured pee. I notice at my DCs' activities such as gymnastics which are fairly sedate, there are masses of water bottles lined up at the edge of the sports hall, and the children simply don't get that sweaty in the class to have to drink through a bottle. Runners are more likely to have issues with over-hydrating on water and not replacing lost electrolytes than to simply not drink enough.
While I found a 750ml bottle useful on my desk as a teacher because talking for 5 hours a day in a warm stuffy classroom is drying, too many students were a PITA with their bottles, fidgeting, leaks, wanting to refill them, needing the loo... If they run out mid-lesson, they are not going to dehydrate to a dessicated husk in the next 45 mins of sitting down. 
A bottle stashed away in your bag for when you need it is fine, but people can be irritating with them when they are out.
Coffee culture evades me completely. I've never understood its levels of popularity anyway. I miss nice cafes with good cake, not loud wooshy coffee shops with overpriced sickly cakes and their whole new language to over complicate things.
Maybe some people didn't drink enough in the past, but there was value in pausing to take breaks that has been lost in recent years. It is sad that teachers (insert alternative profession of choice) don't get the chance to physically and mentally recharge for 15 minutes in the staffroom any more. Water/ soft drinks companies have done a great job on publicity to maximise bottles water sales and convince people that they have a need to drink regularly. We are in a cycle of convenience replacing rest. Maybe in the absence of smoking, bottles and cups replace the fidget factor of smoking. We have lost a lot of drinking fountains that could be utilised directly. I can only think of one at a leisure centre and had to show the DCs what to do as they haven't seen that type elsewhere. Most other types need cups and bottles to fill. I don't know if the drinking fountain declined from over zealous hygiene fears. I've very recently heard of a grant funding new ones locally.