How is “that's why” used?

In Paulie (1998), one line is: “Because you're a loser, that's why.”

Which movie is “that's why” from?

The clip at the top of this page is from Paulie (1998).

Because you're a loser, that's why.

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Used to say that what was just mentioned is the reason for something that follows, or that it explains a situation.

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Used to say that what was just mentioned is the reason for something that follows, or that it explains a situation.