We know that we should operate the aircraft in accordance with the procedures specified in the Flight Manual. Has anyone ever seen a modern Flight Manual which states that the pilot should use a dipstick to determine fuel quantity?
A Cessna or Piper wheelplane on the ramp is pretty straight forward, but an amphibious high wing plane will require a tall ladder, and a floating floatplane is a real challenge.
Fuel quantity indication is required by the type design, and therefore must work. If the pilot suspects it is not working, the aircraft is not airworthy. Now, how the pilot "suspects" the accuracy of the fuel quantity indicating system could take us back to the use of dip sticks.
Happily, some types, like my Teal, have the dip stick permanently installed in the tank, and easily visible through the filler neck...