They may not cause standards to drop for English proficiency, but they can add unneeded stress to other students.  Many courses in STEM and Business have a number of group projects.  Having an individual who may be brilliant in mathematics, but atrocious in English writing, can be dead weight for any shared group work where time is spent deciphering their notes and rewriting them correctly.  Or if they simply do not understand the translation of the definitions, this in turn slows down the class by burning time that could be used for examples of concepts and other lessons relevant to the topic being taught.

Been there.  Done that.  Not fun.