Yes, for some light airplanes a constant speed propeller is not required, but if it is simple enough and you get sizable benefits (even 10% more range), then wh

Yes, for some light airplanes a constant speed propeller is not required, but if it is simple enough and you get sizable benefits (even 10% more range), then why not? There are many planes in Europe that have the cruise speed much higher than the best climb speed. The best climb speed is around 100-120 km/h for light planes, while several plane models have the cruise speed over 200 km/h, up to 250 km/h. I am not aware of any plane with cruise speed below 200 km/h to use constant speed propellers, they have fixed pitch propellers, but the faster ones have in-flight adjustable pitch. I personally flew 7-8 different models of planes, only one with adjustable pitch, but they were all in the LSA class and const-speed is not used there.