Constructing a new world filled with interesting climates, cultures, and characters is a lot of fun, but it also requires a great deal of work. There are so many details to attend to in order to keep everything fresh and interesting. One of those many details is the societal values of your various cultures.
This is something that has always been prevalent in sci-fi and fantasy, but it really didn’t hit me until I started playing Mass Effect. Each of the alien races have a certain defining characteristic, a societal value that defines them as a culture and/or species. For the turians, honor and responsibility. For the asari, it’s diplomacy and psychic awareness. For the salarians, it’s scientific achievement and espionage. For the krogan, battle and conquest. Granted, part of this distinctness comes from being nonhuman; many such races have an overarching characteristic that gives people a starting point in order to relate to them. But even human cultures and societies can have a defining value or values.