In the real world, everyone's thoughts aren't perfectly put together. And they're not always something you'd want to listen to. While they look corny because of the fact that it's scripted, it's something you WOULD hear in the real world. Personally, I find it more annoying when scripts are written too perfectly!
What they should do is hire a couple more writers especially for speeches, because they DO sound very similar. The actors can only put their own touch on it in so many ways.