I am not talking about individuals liking dairy but rather the aggressive celebrity endorsement surrounding dairy in the West, and the invention of substances like Lactaise, creating a false reality where dairy is fabulous for everyone. Even you seem to believe people get osteoporosis without milk, but there have actually been studies linking dairy consumption to INCREASED osteoporosis, not the other way around. Caucasian women have a similar risk for osteoporosis to Asian women, apart from African Americans and Hispanic population, despite milk consumption being normative in most Caucasian societies.
I'm saying people get osteoporosis without adequate types and amounts of calcium. And milk, cheese (made out of milk), and yogurt (also made out of milk) are all winners in that category. For some reason, even high vegetable diets seem frequently deficient in calcium and vitamin D. Vegetables have calcium.. Milk contains calcium, vitamin D due to law, complete protein, fat, and carbs. It's cheap, and readily available, and necessary for many people that are living on a poor man's diet whether you live in a foodie mecca or in a food desert in Detroit.
Weight bearing exercise is also omitted from many women in general, which tends to make them prone to osteoporosis. Genetics play a role as well. So calcium isn't really the only factor--but then people don't tend to drink milk solely for its calcium properties. Milk is in nearly all dairy products unless you pay 2-5x the amount for froofy whole foods stuff. For lactose intolerant people, for like $2 more you can buy lactase-treated milk and it's still far cheaper overall. So, yeah, it was widely advertised.. because it's the cheapest and most agreeable thing to advertise. I'm sure the dairy industry was thrilled and had lots of says, but advertising isn't invalidating to the product. Kids aren't going to start magically liking collard greens, and neither are many adults. Not all adults even like milk and it's super popular. When you're thinking bigger terms and globally, you have to make something that's great for all types of people. Milk, cheese, and yogurt get along with populations far easier than collard greens and bok choy--and milk has added benefits of complete macronutrients as well, and being easier to access and cheaper. I completely get why it's popular. And it tastes good and can be cooked with and used a hundred ways. THere's really only so many ways you can dress up collard greens though. There's not much versatility there.
I've seen the studies about dairy increasing it, but I also doubt that those studies say the recommended amounts are what cause the increase vs an overload consistently in the diet.
While I respect the general tone of your post, I also have to disagree with you that acne is principally a hygeine issue. ...while proper hygeine helps, both high sugar diets and dairy consumption have been linked to chronic acne. Not in all people, which is why the evidence is inconclusive, but removing dairy has worked for a significant number of people.
Diet is frequently suggested.. no study has said, "Yes, this food type causes this for sure." Nothing's for sure in science.. but avoiding nearly all sugar and dairy consumption to cure maybe 2 more of the blackheads you have? Unless you're having allergic reactions, chances are that intervention is only going to be effective for a very select group of people. No harm in trying, sure, but I don't see huge benefits in comparison to using a bit of zinc or sulfur on my face since I have to do that whether I eat those things or not. No sugar didn't give me results. No dairy didn't change anything. And I'm really not alone in that.
Same with mucus. I have met people who are congested nearly 24/7...instead of taking excessive amounts of Claritin, it might do them good to at least try to eliminate dairy.
If their allergies are to pollen, or a certain tree common to the area, or to everything, or if they're dehydrated (many Americans tend to be), it doesn't matter if you drink milk or not, that factor isn't going to make congestion disappear. cutting out milk doesn't stop seasonal allergies or other conditions. It might exacerbate them, sure, but if you're stuck taking medicine either way for the condition I don't see the huge difference in drinking milk then. If I feel super congested that day, I don't drink milk typically, but I also don't need allergy pills as often as I once did. When I needed allergy pills I needed them whether milk was adding icing on the cake or not. The whole damn cake's still there even if I scrape that icing off.