语, mostly goes for listening, speaking with specific pronunciation. --
文, mostly goes for reading, writing with characters. --||--
In Asia, many languages use characters but with a bit different structures or grammar. That's why we call them as 文, such as 中文, 日文。--
However, Chinese has too many different pronunciations even with similar structures. You can't use one "中语" to represent all the different pronunciations. That's why we don't use "中语". It doesn't make sense.