I’ve always been extremely suspicious of constant water consumption. No other mammal seems to do this. Even the ones that require a lot of water like horses will only drink when they’re thirsty or while eating.
The point is you shouldn’t wait to drink until you feel thirty. That’s too late. Your muscle has been consumed by then.
No other mammal eats cooked or baked food. Raw meat or raw plant contain more water than our food.
Tl;Dr blame Gatorade marketing.
The book "waterlogged" does a good takedown of the myth. Basically only you need to drink when you are thirsty.
Most other animals have typical lifespans that don't top two decades.