The idea for the drink is to provide the hot chocolate with marshmallow experience without the hassle. And, if you want it to be actually hot, you can always just heat a cup of it in the microwave.
I suppose a chilled cup of Chocolate Marshmallow milk also works out better if you live somewhere (like California) where winter seems to have just passed you by.
TruMoo Chocolate Marshmallow milk can be found in the dairy section at major retailers nationwide now through February. If you need help finding it, you can try your luck with their online product locator at http://trumoo.com/store-locator.