Url Changes To Ebay.com

I notice that anytime we post an ebay URL to the local ebay (dot ca) it is altered to dot com. Why is that? As a canuck buyer I am logged into dot ca because the items I see are filtered for my locale with the DIFFERENT trading rules that apply to my area.

If someone post a link to the dot com site, that's great, we can still click on it and see the item, the same applies the other way around.

I'm curious more than anything, I mean I'd prefer that items listed on the dot ca be left that way but I just wanted to understand why.

It's easier to ask here than think about it for another year. My curiousity got the best of me. Thank you.