Thermometers in the kettles are really a matter of personal preference.  Some brewers like having the convenience of mounted thermometers on every kettle.  Some brewers prefer to use a digital quick read thermometer and not have that rigid probe in the way of stirring the kettle.  We will gladly install thermometers in 1, 2, or 3 of your kettles based on personal preference.  Some systems ship standard with thermometers in 2 or more kettles (refer to the options list for details)