Languages change all the time, adding or removing meanings from words isn't that remarkable. As for why, it's the same reason people make substitutes for a lot

Languages change all the time, adding or removing meanings from words isn't that remarkable. As for why, it's the same reason people make substitutes for a lot of things. I have coeliac disease and cannot eat any gluten-containing bread, so I make substitutes using various gums and binders to replace the gluten. Even though it isn't the same as a gluten-containing bread it's still useful. Same goes for alternative milks. An emulsion of fats and water is a useful substance even if it doesn't come from an animal. It binds tannins in tea and coffee and has a nicer mouth-feel than plain water in breakfast cereals.