I know the Learjet 35 ops manual recommends using Prist. Will the plane fly OK w/o it...99%...sure. But there was a crash several years ago relating to the icing up of fuel and Lear then said that you should use a can for every x amount of gallons pumped into the aircraft.
Obviously, there are other aircraft that still use it, but I know the older Learjets definately purchase the little cans of the stuff.