Young babies drink milk from their mother's breasts.
and / or
Those who can't handle mead or ale instead drink milk.
and / or
Milk in Skyrim will restore a Warrior's resource for hard-hitting sword swings. Those who require Milk for this purpose would likely be lower-level, and inexperienced.
"Bread and cheese is gude to eat when folk can get nae ither meat.
Bread and milk is bairns' meat: I wish them sorrow that be it."
Seems to refer to a "milk drinker".
Another Example: "What do you think of that, Mr. Pajama-Wearing, Basket-Face, Slipper-Wielding, Clype-Dreep-Bachle, Gether-Uping-Blate-Maw, Bleathering, Gomeril, Jessie, Oaf-Looking, Scooner, Nyaff, Plookie, Shan, Milk-Drinking, Soy-Faced Shilpit, Mim-Moothed, Sniveling, Worm-Eyed, Hotten-Blaugh, Vile-Stoochie, Cally-Breek-Tattie?"
2. Heh, Those hippies are nothing but a whole bunch of cockholstering, bootlicking Milk-drinkers.