I haven't flown the Cessna 140 in over 50 years, but as I recall, you can stand on the strut next to the fuselage and get a good visual or dipstick check.
Wonder if I can still do that?
I do not know of a light aircraft I would wish to fly in without checking the tanks visually or by dipping the tank. Corks fill with gas and sink. Sealed floats develop cracks and sink. Mechanisms disassemble themselves. Even capacitive systems get cantankerous.
Better safe than sorry.