>I think this might be because the "rush" comes from the things we buy, not the saving itself.

Yep - the instant gratification of buying something for $100, is far more satisfying than investing $100 

>There is definitely a skew here.

Definitely a skew for disposable income. Interestingly though;

*The average annual average salary in the U.S. is $60,575. The median annual salary, which is often less skewed by outlying numbers, is $56,420.*