Because I ride hard and like to drink cold fluids when working hard.

For those asking about hydration on winter rides, I like to ride fatbike metric centuries in the winter, so I need the hydration on the ride. I've also done long sub-zero rides (25 to 45 miles). All of this is long-term planning/training for the Arrowhead 135.

Edit - back to the double-walled thermal bottles... this is what I need to use for the Arrowhead 135, along with coozies.