Grammer is a waste of time; you'd understand me irregardless
Grammar is the structure of language. If there was no grammar, then what you say would lack a rigid structure. Lacking grammar would therefore severely hamper my understanding of what you are trying to say.
Formal language is important in both research documents and documents that can be used for legal purposes. If something can even slightly misinterpreted by a misplaced comma, you might find yourself on the receiving end of a nasty lawsuit.