>In my experience as a college student, it is exceedingly rare to use cash, especially cash in amounts greater than $5, for anything other than crime.

You must live in a bubble then. I live in a beach town where there are many small restaurants, souvenir stores etc. that only take cash. (It's not a problem for the tourists because there are many ATMs). Once you leave your bubble there are also farm stands, yard sales and so on.