How necessary are aftermarket gauges in gas motorhome

I have the ScanGauge OBDII that I leave connected at all times. With it I continuously monitor my water temp, my transmission temp, my charging voltage, and my air fuel ratio. If there is a problem developing I can usually catch it before it gets out of hand. My dash board digital readout monitors my oil pressure so I think I have most all systems within a quick glance whenever I am on the road.
The ScanGauge can also be used to read and reset any trouble codes that pop up on my RV or my toad during a trip.