I recall one incident from my youth in which I, as a passenger, was politely "asked" by a rather burly member of the NYPD to exit the vehicle I was sitting in. What makes this incident stand out is because he assisted my exit, via the passenger side window. Long story short, the driver's car apparently matched the description of another car which had been seen leaving the scene of an armed bank robbery, and while neither he nor I looked anything like the two black males who committed the crime, the officers were not going to take any chances in finding that out.
Point being, there are all sorts of reasons why this might happen. No way to guess them all.
