Shipping to Canada

Can someone answer this question for me. When I look at the parts for sale on the forum and am thinking of buying them I see in the sellers comments they will only ship their parts to the lower 48.I can understand this for bigger parts like body parts but why not smaller parts like windshield wiped arms and gauges I have wanted to reply to some of the for sale posts but after reading the write up I move on to another post Thanks for your help