Okay... let's say we should avoid a cashless society and encourage people to carry cash. Why is a $500 note useful? If you look at businesses today, you'll find several with signs that say "no bills greater than $20 accepted." If you think it useful to keep cash stuffed in your mattress in $500 notes, and there's a massive disaster that shuts down all the banks... where are you going to convert that $500 into everyda…
Since the Fed, which issues currency, is, in large part, the banks themselves, if a disaster causes a general banking collapse, you've got bigger problems with the value of your cash than whether you can convert denominations.