First of all, we live in a capitalist economic system, not under a capitalist government.
Although we call our system capitalistic, it's actually a mix of capitalism and socialism. Pure capitalism gives everyone the right to earn, spend, and do business with little or no government controls or interference. It depends upon the entrepreneurship of individuals to succeed or fail.
In our mixed economic system, the government exercises some controls over business and interstate commerce. It provides Social Security for retired and disabled people, education for children and economic help for the poorest people. In some mixed economies, government also provides health care and other services for its people.
As you can see from this site, very few countries are socialist. And although they have strong government controls, they too are adopting more and more capitalistic programs.
Why do people want to live in an economy that is mostly capitalistic? They enjoy freedom to go and work where they want. They can realize their dreams and make a lot of money if they are educated, personable, and hard-working.