What does it mean when a person is

They likely don't trust you unless they appear that way to everyone. Many possible reasons. Someone may have great wealth, but don't want others to take advantage of them. They may be involved in something illegal or top secret. Some are natural introverts and have a limited need to socialize and feel safer keeping to themselves and avoiding crowds. If I suddenly came into great wealth, I would have reason to keep that a secret and only people at the bank would have any idea how much I had.