Canada has a shitty postal service! In 15 years or more of doing mail order I have lost more packages in Canada then anywhere else in the world! I insist they be insured or I will not send them.
I've only ever had one seller actually tell me that they won't ship to Canada. Half the time if you simply inquire they will. I think this is as much a method of filtering then anything else.
If I am really keen on an auction, then I will enquire about shipping out to me. I find it is actual shops selling through eBay that are the hard asses that won't ship international or even sell international and ship in the U.S.