The problem is breaking people away from their cultures that their languages are so very based on.
''Culture'' in a language can mean the terms included in it, depending of the language. For example, in mexican spanish there are terms as ''wey, cabrón'', in chilean spanish there are terms as ''weón, fome'' and you can see that in Mexico people will not speak as people in Chile does & viceversa. Another example, if you already speak mexican spanish and you want to go to Russia, you can perfectly learn russian and its terms while keeping the mexican terms. If i'm not wrong we can see that there's not much problems.