Why is "rate shopping" considered a waste of time?

Think of a see-saw. If one side goes up, the other side moves down. The same applies to mortgages. Since we all are given the same rates with which to work, it is a matter of balancing costs. If rates are higher at one company, their discount or closing points will often be lower, Conversely, if the closing points are high, the rates are generally low. We all have the same center of balance therefore we are all at the same point in terms of cost. Your decision must then rest upon service and location of service.