A completely different reason
Benny Howard, the hero of the 1935 National Air Races, related this story to me in 1969. His production high-wing cabin aircraft (DGA-8 thru DGA-12, all similar save for the engine choice) had no dihedral and had no need for it - EXCEPT for an optical illusion that made the semi-elliptical wings appear drooped when viewed from behind. He thought this was unattractive and might have hurt sales.
So when he revised the design to accommodate another pax, designated DGA-15, he lengthened the wing struts a few mm to raise the wingtips maybe 2 cm. This made the wing LOOK straight, although it had no effect on flying qualities.
PS - probably the worst-kept secret of the day was that his DGA designation stood for "Damned Good Airplane"