You're right. I get that for things like old coins because no one uses them as currency anymore. $2 are still somewhat readily seen and used in everyday stores. If you handed a store a pure $50 gold coin from 1915, I don't think they'd accept it.
I don't know I guess I understand why it's "worth more" but I will also laugh at people who spend over $10 to have a $2 bill.
Peace, Love, and Radical.