That's a plausible theory. I suspect another reason people save less (outside of their retirement plans) is the prevalence of two-income families among middle and upper-middle income families. Apart from retirement, the most important reason to save is to provide a cushion against emergencies, especially job loss. Nowadays, however, the working spouse is the safety net. Folks have a lot more hang time than they used to.
The third traditional reason to save was for a big purchase, but today we just put it on a credit card.