[thaumasiotes]

> say you need to drink a lot of fluid because you are really active

If you're replacing sweat, wouldn't you want sports drinks?

https://www.gocomics.com/peanuts/1969/03/27

But anyway, in most cases, the fact that drinking milk doubles as a source of food is clearly a benefit. It's hard to explain a common behavior by reference to a rare circumstance.

[seanmcdirmid]

Sports drinks aren’t really good for you, but you definitely can drink a lot more of them than you can milk.

[thaumasiotes]

The idea of sports drinks is that you can drink them without getting water poisoning. This is only a concern if you need a lot of water because you've been sweating a lot, but I thought that was the scenario you were pointing to.