A grammatically correct way to ask someone a question would be:
Why are you still here?
If I want to make a statement (instead of a true question), such as, You've been here too long or Your comments are annoying, or You're either a troll or a quarrelsome person, would "Why you are still here" (meaning- why do you continue arguing with everyone) be acceptable in a conversational English?
Do you know why you're still here? is grammatically correct, but I don't want to know if he knows, I just want to express an annoyance with the person.