"drink some milk"

This is kind of a random rant, but, over the past few days i've been seeing so many people say "just drink some milk" when someone says they're sick or having trouble sleeping or something lol. like for any sort of illness/uneasiness these people suggest this stuff that isn't even meant for our bodies....... It honestly baffles me every time. where did this myth even come from? and does this bother anyone else as much as me?