they do it to cover their ass, simple as that.
As the importer of the goods, YOU are always the sole responsible person for the goods that come into the country.
This is in the eyes of Canada Customs.
As consumers in this society, we "EXPECT" to get our goods when we pay for it. This is the North American way.
A LOT of stores take flak from international customers when THEIR customs seizes the goods because they weren't diligent in properly importing the goods. As consumers, they feel it's their "right" to bitch out the retailer and to ask for money back because they claim "it wasn't sent properly."
Retailers shouldn't be responsible because the importer wasn't diligent in setting up their end of the importation process.