Iains said the purpose of any language is to communicate and I agree. The rules of grammar are an attempt to agree what precisely is meant by a construct, but every language is too wild a creature to be so bound. Richard II has been referenced of late in other threads, and it contains the wonderful rejoiner "Uncle me no uncles". In context at least, absolutely clear what it means, but I doubt if it abides by all the rules of grammar. Similarly therw was a reference to 'Under Milk Wood': an exuberant display of language whose meaning comes across though many rules are broken along the way.

So rules have their place and it would be foolish to ignore them entirely, but they are to my mind the servants of language, not the overlord.