I believe they are this way because, largely, they are people who find themselves in a situation where they make so much money so easily, they feel guilty.
And thus they try to expunge their guilt by transferring it on the rest of society. They assume that anyone who has money acquired it as easily as they did, and therefore they must help to redistribute it to those less fortunate. But not at the expense of their own lifestyle, of course.
And you must remember, with actors it’s all ego-—an intense need to have a giant ego stroked, constantly to affirm their worth. So, they surround themselves with people who insulate them, tell them what they want to hear, and never say no to them. Fan adoration only reinforces the whole ego deal and in time they begin to believe their own press.
They lie for a business. They pretend to be what they aren't. They live fantasy lives. Need I go on?