[Okta20]

We learn about all that stuff at school in history lessons (about three times over the years, depends on what school you're on). And of course you'd be able to learn about it elsewhere, if you're interested, but that's the point: if you're interested. Most people aren't. And the 3. Reich is something that we cannot allow to be forgotten, ever. Because History has proved to repeat itself over the centuries.
Also it's necessary to understand your country's history in order to understand what it's like today and why it's the way it is. And the 3. Reich is the part of history that influences us most, along with the division of Germany after the war and the reunification in 1990.