Unfortunately, some bike shops often sell people the wrong size bike just to get rid of stock that's been sitting around for a while. I worked at a shop a few years ago and would literally get into screaming matches with the owner because of this. One time, he tried putting a dude who was at least 6' tall on a 52cm road bike, telling him that "once we put a longer stem and seatpost on this puppy, you'll be as good as gold!" and also feeding him a bunch of crap about how the smaller bike will actually fit him better because he had short legs for his height (which he did not). When I managed to privately talk the guy out of it, the owner *****ed at me because "We've had that bike on the floor for far too long!"