To accent, or not to accent

Something I have never really understood is the use of accents in films that take place in a different country. What am I talking about, you might ask? Well, take "The Reader" for example. The movie mainly takes place in Germany, yet all of the dialogue is spoken in English....with the actors employing German accents. My question is, why bother? You're already not following things realistically by not having your actors speak fluent German so why bother to speak in accent at all? It's not just the Reader that does this...pretty much any movie that takes place where English is not the primary language. This got me to wondering about things..as a singer of opera I had to learn to read foreign languages phonetically and also to understand what I was singing about so that I could properly interpret the song. Why don't actors have to do the same? Oh, I know the typical answer is that the viewer is too lazy to be bothered to read subtitles...but seriously--why even be bothered by the actor's accent if it doesn't 'sound' right then. It's inconsistencies like these that frustrate me, but don't keep me up at night. And that's my 2 cents!