From the Rules -> Staff -> Doctors:
Taping Injuries: There is a small chance that a player's minor injury can be taped up immediately, and he will be able to return to the game at the start of the next quarter.
If this is a speciality of certain staff members then adding it into the game engine as a regular skill of normal doctors would render the speciality useless, without mentioning the outcry from people who have shelled out for these doctors!