Part of it is just American culture and American salesman who care more about the commissions and a quick sale. I know a couple sales folk who are genuinely into cars and BMWs, and although may not be 100% perfect on knowledge, do a very thorough job of going over major features. Unfortunately, the rest of them know just enough to pass by and talk more about how much fun they had at the Greer Plant when BMW demos the trucks on a track.
In Germany, most if not all salespeople are salaried and not on commission. I've gone to BMW dealerships there, and never been hassled. If one has a question, they're there to answer your question and they know their stuff, but won't pressure you into anything (the same applies to the parts dept.). It goes beyond BMW too........even folks at the Adidas shoe store took the time out to measure my feet and explain the whole shoe-buying process!
Maybe next time I go to Germany, I'll ask to test drive a 1er hatchback or something.