If they can't trust the people they work with then nothing gets done because people can't rely on each other to get what they have to get done, done. Another important aspect of honesty is that people like to be able to trust one another. Friendship, in most cases, derives from one person trusting the other and therefore liking that other person. Trust is also important in a family. Family members need to be able to trust each other so that they can get along.
All families have trust between family members.
Another important thing about honesty is that if someone lies, cheats, or something else dishonest, then they will have a sense of guilt. Anybody with a clear conscience will be bound to feel better about themselves. Anybody who feels better about themselves will do whatever - fight, write, sing, type, play, run, etc., better. People with a clear conscience are the ones who do well on earth. The only people who benefit by lying are Politicians.