Why is there not a universal way of writing anything that is not ambiguous and can be read by anyone that understands the 'language'? Because humans have a tendency to defy attempts at classification and constraint. Constructed real-world languages (Lojban, Esperanto) haven't really taken off, while non-constructed languages mix and match whenever they feel like it ("le parking", "Schadenfreude"). The same is true in maths: people use what is easiest.