Coincidentally, I just got fed a YouTube video about this! I think this might be a reproduction of the German tradition of "Kaffee und Kuchen." This may explain why there are so many cakes and why they're full-sized slices; to a lesser extent this might explain the brief serving duration. In short, Germany continues to have some form of an afternoon coffee tradition, and it specifically includes cake.


Disclaimer: As synzero said, you may have vastly more experience in Germany, and actual residents of Germany should feel free to chime in. Then again, I did stay at a Holiday Inn Express last night...