Sister cities

What is the point of cities having sister cities? For example, I went to Sebastopol California this weekend and noticed that it had a sister city, well actually it has two, Yamauchi, Japan. I started thinking what does the sister city status really mean, whose idea was this and who in Sebastopol knows what their sister city is? So I took a quick look over at wikipedia to find out that sister cities are used to promote commerce and cultural ties. Really? What commercial and or cultural ties could exist between Sebastopol and Yamauchi? As it turns out there was more to it than I thought. Sebastopol, and Yamauchi too I guess, won an award in 1985 from sister cities international for best first year, though I am not really sure what for...