Pirates don't drink milk

I'm not sure if it's a mistranslation but in chapter 1 Shanks drinks Luffy into drinking milk than tells him "A real pirate would never drink milk"

And I think I just realized why, similar to why Zoro refused to be slashed in the back maybe drinking milk is seen as a sign of weakness.

Milk in the world of One Piece somehow has healing powers, so what if it's seen as a sign of weakness but taking your wounds like a man is seen as noble and healing them with the powers of milk is seen as cowardly.