I don't assume anything... I just observe.
What I observe is that pretty much the same people (from the same security firm) screen my luggage at the airport and my bag before I get into a night club. I don't like it a clubs, but accept it. But I find it close to unacceptable at airports. I've seen a lot of incompetence, lack of respect and abuse of power at German airports (especially at FRA).
In Canadian airports, the pre-boarding screening is also partly done by private firms. The situation is hardly better. I've seen a huge difference in handling there as well. Most of the time its is very professional and the standards of CATSA at obviously higher than by the Bundespolizei. I think that a major difference, is the the on-site oversight remains under the control of the CATSA in Canada, whereas in Germany, the Bundespolizei is only there for show. They just stand there (if at all), but don't seem to supervise the screening activities. This observation may be wrong, as we, as passenger, hardly know what goes on behind the curtain, but it would explain the service quality in both countries although but employ private firms.
I couldn't care less about the screening itself; it beings little more than the feeling something is done for security for those who somehow need that feeling. What I do care about is how my belongings and myself are handled in the screening process, what ever that process may be.