About the "why?". Ever try to discuss the artifacts in a museum with the guards? I believe the guards are lurking among the oil paintings because it is a reasonably good job that they can qualify for and not because they have a great love of French Impressionism. The same may be true of many of the border protectors.
In recent years arrival at Yvr has been the worse. Fortyfive minutes of interrogation: "Why are you here? Who do you know? Why are you really here?" I give up. I just don't do Canada anymore. They have finally managed to demolish their "nice" image.