1. We still do. Men wear a robe (actually a cloak, such as a tallis). To make it more convenient, it now has sleeves. During the 20th century, the style for men moved towards shorter jackets, with longer jackets (frocks, kapote, etc.) only for more formal usage (among goyim, note that the Netherlands king wore a kapote when he took his oath, and most men work similar jackets for the wedding of the Prince of Wales). Long jackets lost popularity when King George V stopped wearing them in the 1920s (Jews couldn’t care less about him, so we didn’t get the message).
2. It appears that jackets, and pants, became a lot more popular in western Europe at the end of the middle ages (perhaps due to the climate suddenly got colder). Robes, without pants, are popular in many countries. Since the Americans and Western European conquered the world, their fashions become more prestigious.