Should a baker want to give a bread a softer and smoother texture, fat can help because it retards gluten development. (The greased gluten strands have a more difficult time latching on to each other and therefore are less effective in forming a structural network). A fat also adds flavor, richness, nutrients, calories, and if it is butter or lard, then saturated fatty acids. Butter and margarine also lend color.
** Asian Recipes