What do millionnaires work for?

What do millionnaires work for? -- People work because they need money to live. What are some other reasons that people work?
There are many kinds of millionaires, and why some millionaires still working hard? I figure out some reasons.
Most of the millionaires are inherit their family. Some of them think that is not what they should get. And they think they have to work hard for their own life, instand of using what they’ve inherited. I have heard that some young men donate all they inherited. I think perhaps they want to show others they can earn as much as their parents.
Some of these millionaires own their own company. If they don’t work hard to maintan his company, it would be broken up.They’ll lose their families’ company, all their money and most important, lose face.
Some of these millionaires inherited houses and acre. They still have no cash. So they have to work for their living.
And finally, there are still some millionaires work. It seems no reason for their works. And they don’t know why,either. They like to work. When they don’t work,they’ll feel anxity.And that is why they can become millionaires.