I am not German, but I know that in German, the definite article is used more often than in English, and in places where it doesn't make sense to use it in English. For example, my name is Samir, and in English I would say: "I am Samir", but in German I would say: "Ich bin der Samir". In English, saying "I am the Samir" would imply that I am some famous personality, like "THE one and only Samir", but that is not the case in German. Every language has its idiosyncrasies :)
Newer German learning methods and books seem to avoid using the der version probably to make it easier for new learners, as German would appear closer to English that way. That might explain why you have never heard it before. Also, the Germans themselves seem to be using the versions without der more often, probably due to globalization. But if you watch German TV or play computer games in German, you will still encounter the der version. I also asked a cousin of mine from Austria, and she says they still use it, but not as often as they used to.
Here in the US, I go to a German language Meetup.com group. I have heard one of two people use the definite article when introducing themselves (ie "Ich bin die Emily".) I also heard it used in a German video series for German students. (ie "Ich bin der Daniel.") I'm still not sure when it's used, so I have decided not to try to use it myself.