Why is wealth and greed portrayed negatively in American movies?

In many American movies, generosity and family is portrayed as something to strive for and greed and individualism is something to be frowned upon. This is especially true in Christmas movies, such as It’s a wonderful life (1946) and Family Man (2000). But also in non-christmas movies such as Trading places (1983) and Wall street (1987).
But considering that USA is built on capitalism and has a culture where money and careers are very sought after, why do many movies try to make us believe that Americans don’t like or cherish wealth and greed when they actually do?