I suspect it may have something to do with Weight and Balance. Not knowing about Piper Cubs super or otherwise, I cannot comment on that particular case.
However, you put two slightly porky people in a 150/152 and a safe fuel load it will be close to or overweight, depending on the airframe.Iignoring the fact thait it will be rather snug in there. Add a damp grass strip to increase the take off distance. It all becomes rather interesting and insurance companies begin to take notice when aircraft go through the fence at the end of the strip.
Whereas a 172 or a PA28 will be well within W and B and can cope with a couple of pie eating aviators.
My instructor, bless him, was a bit on the large boned size had problems flying certain aircraft because the W and B shifted too far back and he began to loose elevator authority. He could never fit into a cub, so problem solved.