You couldn't do this without getting sued for discrimination, which is why it needs to be mandated by law.
No, this is mandated by greed. They don't offer these services to Koreans, Chinese, etc. It 's a money thing, they don't want to help them, but take their money. And, what happens is that they get soo used to having it like that, that they expect everything that way. They will come in to certain and places and say in perfect English "Excuse me, you speak Spanish?", and if they are told "No", they then catch a hissy fit. And some places, you have to put things in writing in English, like filing charges, but they will ask, "Why can't I write it in Spanish?", because it's a legal document.
What you have now is huge pockets of people who are now incapable of communicating with the outside world, unless they "Speak Spanish". They can't read signs, many don't know how to get to their house, they don't know the address. All they know is "Down the street from the Popeyes". And then, many such as El Salvadorians, Hondorans,Guatamaleans are illiterate in their own language, and look at learning as for the birds.
SImply it would make way too much sense to have everything in one language, and far more green. Less ink used, less paper, less options to set for electronics, and less excuses to be heard.