Office time rarely has the same value as face time. Offices are too often a place to hide. If the boss really has superior expertise. If the boss is only marginal, then maybe the office is the place where he or she is least likely to do damage. Otherwise, most of what gets done in offices either could be done by someone who has a much lower face value or, as is often the case, work that really needn't be done at all.
Pagers are a variation on the theme.
Pagers are too often an excuse to be someplace you shouldn't be. The Employment of Face Face time puts the boss in direct contact with the customer. Even at the lowest level, the boss's face has incredible value. They wanted to know that when they walked in the door, the owner, not a clerk, cook or assistant, would call them by name. A restaurant that serves mediocre food, but where the boss is omnipresent, will beat out a fine dining establishment where the boss never makes an appearance.