Taking a job across the street means taking up another profession. This is the whole point: due to the economies of scale, taking a job across the street means

Taking a job across the street means taking up another profession. This is the whole point: due to the economies of scale, taking a job across the street means literally restarting your career if you are "lucky" enough to find one and almost your entire life if you are less "in luck". A comparable job would be in another state, or even continent. Hence forced mobility. It is all about making sure cogwheels are replaceable by ensuring they are actually replaced on schedule.