Why no unsweet iced tea in Canada?

I was told something today which disturbed me to the bottom of my tea-drinking soul. I stopped by the Tim Hortons near work and ordered an unsweet iced tea. Turns out the store manager is Canadian and was amused by how many people in the United States drink unsweet iced tea.

"Did you know you can't even order unsweet iced tea in Canada," he said. "People wouldn't even know how to make it for you. All the iced tea in Canada is sweet."

I'm sure that last part was hyperbole, and mind you the manager wasn't hating on unsweet iced tea. After all, it's far more healthy than almost any other cold beverage aside from water.

But I'm now curious. Why is unsweet ice tea not a thing in Canada?