Human beings also do not always say what they think. For Highly Evolved Beings not to communicate what they're holding in thought—which is different, by the way, than outright lying—would be seen as a behavior without benefit.
What good is holding a thought if it is not expressed? And for Highly Evolved Beings not to follow through on what they say to each other or to themselves that they will do, would be viewed as equally without benefit.
A : Why would you hold a thought that’s not very nice? Stop that. Sometimes you’ll have a thought that runs through your mind, but you don’t have to hold it there.