The casual language of which you speak is all perfectly fine - in speech. It is not fine in the written word unless the writer is deliberately resorting to the vernacular, which is also valid. As ever, language is wot people speak in their everyday lives, not subject to the strict "rules" of the grammar police. Enjoy the colour!

I was a good lad at school, bright and literate*. One day, my mate put up his hand and politely asked the teacher, "Sir, can I go to the toilet, please?" Came the reply, "You can, but you may not." That teacher was two bastards rolled into one, and witnessing that exchange left its mark on me. If you understand what the speaker is saying without having to do a lot of mental processing, it's all good and it shouldn't be subjected to snarky criticism.

*The gloss may have worn off just a tad...