It's not all about the absolute ratings, though.
For example, "Stromberg" (a German "The Office"-clone) doesn't have great ratings either, but it does a lot for the TV-station's image, in that case Pro7.
Similarly, I'd rarely watch Kabel 1 outside of some classic movies they have on from time to time, but the GT-Masters broadcast made me watch the so-stupid-that-it's-actually-awesome reality-TV-show Heli-Loggers...
Think of it as a "loss leader" - it might not be profitable in itself, but it attracts customers you'd have a hard time reaching otherwise.