It's always a constant struggle, just like Internet censorship [0]. Politics usually sell it with the "It's only used against terrorists and pedophiles!" angle, while police actually end up mostly using it in drug-related cases.
But it should also be noted that the US had its fair share of influence in eroding the actual application of privacy laws in Germany, by pressuring Germany to modify its G-10 law to appease the NSA [1].
People need to remember that the German BND (German intelligence agency), traces its roots straight back to the Gehlen Organization [2], which was established in alliance with the CIA after the end of WWII.
It's this old shared-history that allows the BND and NSA to work as closely as they do, to this day, bypassing privacy protections of the German Grundgesetz trough designed loopholes and secret agreements.
Case in point: According to German law it was completely legal for the NSA to listen in on Angela Merkel's phone calls [3].
[0] https://en.wikipedia.org/wiki/Zugangserschwerungsgesetz
[1] http://www.europarl.europa.eu/document/activities/cont/20140... (Page 3)
[2] https://en.wikipedia.org/wiki/Gehlen_Organization
[3] https://www.zeit.de/politik/deutschland/2013-10/nsa-uerberwa...