Why is it said that the American people are always on the move?

Why is it said that the American people are always on the move?

Mobility is considered one of the characteristics of the American people. They move from one part of the country to another all the time.
There are four great population movements in American history The first was the flow of popealation from the densely-populated east coast to the sparsely-populated west. The second was from the rural areas to cities. The third was the movement of a large number of black people from the south to other areas. The fourth was from the Northeast and Central North to the West and the South.Another trend which occurs more or less at the same time with the movement to the South and the West is the outflow of city residents from the core cities to the suburbs.