In comparing TeX to MathML it is easy to make a category error. TeX is a human input language. In other words, it was designed to be typed by humans. MathML is a computer representation and was intended as an internal representation and not something for mere mortals to type. Just as RTF (Rich Text Format) is text and can be typed, it is not intended to be typed. RTF and all XML languages, even HTML, are not really designed to be input languages. That is not their forte.