When you define prosperity in large amount of people, it makes you sound like a communist, and America spent decades to avoid that. The other alternative is to sound like a capitalist, which is very much ok by today’s standards.
This is so interesting to me... Maybe it's because I grew up after (most of) the heavy anti-communist propaganda in the US, but the last thing I think of when I hear "communism" is "prosperity in large amount of people".