[Delkaetre]

Eh. I drink milk because I like hot chocolate and because it cools my tea faster. I don't like plain milk.
Milk is the only fat-reduced thing I ever have, because semi-skimmed lasts longer than full fat before it goes sour.
I don't drink it for the calcium, and I could probably use whatever fat it has in it since I don't really get much from elsewhere.

As for 'not intended for human consumption'... well, I'm kind of wary of saying that. After all, humans can and do eat all kinds of things that may not have originally been in their diets during the evolutionary process. We eat a lot of imported exotic fruit like mango, which doesn't grow up here in the cold northern clime. One could as a result argue that mango isn't intended for consumption by humans of celtic, nordic or otherwise non-tropical descent. There are suggestions of genuine differences in tolerable diet depending on lineage, such as the unusually high rate of lactose intolerance amongst particular groups of Asian descent.
Humans specialise in doing things that we were originally 'not meant' to do. Technology alone shows us this. So as long as it doesn't kill me and doesn't actively harm another human, I'll be happily doing whatever it is. And since I'm not lactose intolerant, I'll continue enjoying my hot chocolate.

(And sorry to pick up on this point as well, but a possible additional reason for the vegan/omnivore obesity contrast may be that a lot of vegans don't have a well balanced diet and are more likely to end up underweight. There are a lot of fat omnivores anyway, since there's more processed food available to them. I wouldn't include it in a dairy debate since dairy is only one of a pretty wide range of factors impacting the obesity comparison.)