Because I was too fat
my mother forced me to switch from whole milk to non fat. I hated it. My father would help drink my glass of milk down when my mother wasn't looking
Eventually, by slowing reducing a milk of whole and non fat to all non fat I got used to it. Now I can't tolerate drinking anything but non fat, unless it is hot chocolate.
I am grateful to my mother as I loved drinking milk and the amounts I drank would have been rather pound producing.