I still use milk for all types of cereal.
Though for solid grain cereals, I usually use water to cook, and mix in some milk after it's cooked. But it has to be done right to add milk to, it has to be super thick, that way just the right amount of milk brings it down to an overall smoother consistency.
I have forever agreed that using cow's milk after we are kids is a weird thing to do, but it's habit, and essentially the norm in our society, so it's a hard habit to kick.
I haven't had trouble digesting milk (it's in the European blood-line for humans to keep producing lactase well into adulthood, but it's not universal, and not strictly limited to european ancestry anymore. It originated there, unlike humanity itself), so until it gives me problems, I probably won't stop consuming it.
But I am also using sugar-free Almond Milk more and more - but only for things it's a simple ingredient in, and not a huge provider for flavor. With cereal? Nope. Protein shakes and in bigger dishes? Sure.