Now let's look at Lawful Evil. Suppose a Lawful Evil creature discovered a utopian kingdom with laws that perfectly mandated good behavior. Would that creature cease to behave evilly in order to remain lawful? It seems unlikely. Hence, it is unlikely that there are any truly lawful evil creatures. Rather, there are only evil creatures who can tolerate lawfulness. That makes them simply Evil, not Lawful Evil.
The utopia scenario could also be applied to Lawful Good characters. Put a LG Paladin in a distopia of perfectly evil laws. This forces the Paladin into a hard choice: be lawful or be good? However, that also seems like a conflict it makes sense to throw at players. It seems much harder to conclude what the Paladin's choice will be than to conclude that a lawful evil NPC would choose evil over lawfulness. Perhaps if D&D weren't focused on good protagonists and evil antagonists we'd have to treat them the same, but in general it seems more useful to keep Lawful Good and toss Lawful Evil aside.