Because a large percentage of Germans probably speak English so you can still communicate with them without learning German. This is not the same as a single language country.
Clearly you can manage but I stand by my original opinion that I would not approve of hearing such a story from an immigrant.
I've been a tourist in Germany too. Basically, if the German person you're talking to is university-educated, they speak English, and probably extremely well. If they aren't (like the cashier at the supermarket), they probably don't speak English much at all.