"More is always better"? Hardware solution to a software (lack of skill) problem"

More seriously, systems failures a Long Way From Home over Moonscape and/or not wanting to abort a great flight are good reasons for an independent backup vario. Survival XC soaring using seat of the pants plus altimeter is not fun.

Or just to enjoy the beauty, precision, and sensitivity of the Sage/Schuemann mechanical vario. A stunning device.l