Spoken language and written language are often referred to as two different modes. Spoken language has a structure that is often different from that of written language. Because we use spoken language in different situations from written language, we can often rely on context, gesture and shared understanding, so many of the grammatical structures and devices that we tend to use in written language aren’t necessary.
One mode is not ‘better’ than another mode, and we should be careful not to describe spoken language as ‘incorrect’ or ‘wrong’.