If you don’t drink milk, why do you need a substitute? A substitute that comes in difficult to recycle aluminium-paper-plastic laminated cartons that still contain most of the food-miles and process / handling carbon emissions.
Ok, hipocricy is everywhere and we can’t all be angels over night.
Speaking for myself, I drink almond milk because it tastes better than cow milk.
Also, where I live, dairy comes in those tetrapaks, too.
It's something sorta similar to milk that can be used in roughly the same applications - lighten coffee, moisten cereal, baking, sauces, fold into mashed potatoes, etc.
I prefer the taste of pretty much all nut milks to cows milk, personally.