Not being from the US, this is probably a stupid question. But why can't people in the US sell willingly and freely sell things (legitimate or otherwise) to other willing buyers without government interference/participation?

I guess I used to think the US was the "land of the free" I guess I understood that people used this phrase in a literal way. Im wondering, when American's use the phrase "land of the free" perhaps I am misunderstanding, and it's really generally used in an ironic way?

Can someone please explain?