How do people know that they are rare? I don't even know what bills exist in my country but I know they keep changing them now and then. I wouldn't be able to tell whether it was rare or just a new bill I haven't seen before.
The US has a small set of valid bank notes. It's not like other countries that have multiple issuers, each with their own schedules for when to update designs.
On top of that, this isn't just a design that a person hasn't seen often, it's a denomination. Think of the 500 EUR notes, they were unfamiliar to many people.
On top of that, this isn't just a design that a person hasn't seen often, it's a denomination. Think of the 500 EUR notes, they were unfamiliar to many people.