This is because both of these regions have specific subjective opinions about these areas which reflect their feelings and images. What this means is that both West and East in Europe were influenced by particular political ideologies - West by democracy, whereas East was influenced by communism. Even today, Eastern and Western Europe are quite reflective of those ideologies.
When to talk about the plate tectonic it sound the same as our continents as we see in the ancient days you were having two continents which is laurasia and Gondwanaland
