Well, in textbooks you often learn sentences that aren't very likely to be said. Textbooks often needs some easy phrases to get you used to the language. I'm quite sure the respective phrase in your native language isn't in use either, is it?
Anyway, I can think of two groups of people who use this phrase. The first group consists of comedians, presenters or any other people who are about to give a monologue and who think that they possibly aren't known to the audience/listeners.
The other group are agents and the like who unexpectedly confront you with something and they want to get you into a conversation about something. They might use that phrase just to get your attention.
There are many ways to introduce yourself. Too many, to list them all. I'm giving a few examples below. Note that that sentence you've given might occasionally be used, though.
When joining a group or meeting a person:
- Hi, ich heiße Em1.
- Hallo zusammen, ich bin der Em1.
During a conversation when you haven't introduced yourself yet:
- Entschuldigung, ich habe mich noch gar nicht vorgestellt. Ich bin Em1.
- Ach, ich heiße übrigens Em1.
Or you ask them what their name is and then, of course, they'll ask the same question.
Me: Wie heißt du eigentlich?
You: Ich bin Wasu, und du?
Me: Ich bin Em1.
Your third question is partly off-topic as there aren't much cultural differences between German native speakers (living in Germany and surrounding countries) and we won't address cultures other than German ones.
In Germany, it is polite to introduce yourself. Depending on the situation you should do it right away (like an agent or a presenter).
In other situations you do it a bit later, e.g. when you happened to run into a conversation with someone at the gym. You don't start off such a conversation by introducing yourself, but if the conversation keeps going, you should briefly tell your name at some time.