Less food miles. Less cheap availability of dairy will encourage movement to less polluting alternatives. Less intensive farming leaches less nitrogen.
False dilemma. People don't need dairy milk (a lot of the world is dairy intolerant anyway) and there are alternatives that don't pollute anywhere as much, don't need as much land nor water and which are inexpensive and getting cheaper all the time.
People don’t need a lot of things. However certain foods, like animal products including milk, lead to optimal health. That’s how the Dutch got so tall. So you can drink your diluted nut or grain water. I’ll stick with bioavailable nutrients from animal foods.
"A lot of the world is able to walk, so people don't need wheel chair access in buildings".
"A lot of the world is male/female, so people don't need made up genders and surgery".
... sounds great, huh?
Anyway, where does this "people don't need X" stop, though? You also don't need oat milk, tofu, soy, peas, etc. to survive.
Let's just go back to foraging for roots and berries and see what population size we can sustain!