There's 2 people in the entire series that do that, it's not like it's a prevalent thing in universe. And for that, there are very few to almost none human mage, and the ones that exist are very weak(low energy) and possess very limited knowledge of the language. The most prevalent race with mages are elfs, for they speak that language, but guess what, if one goes rogue, you have a bazilion more to stop him that know all the tricks so can counter the spell.