I don't know why it's such a big deal, but it annoys me that vending machines only take $1 bills. I don't carry much in the way of cash, but when I do, I rarely have a 1, I have a 5, 10, or 20. If I ever want anything from a vending machine I have to beg to borrow change for whatever bill I do have, or I have to borrow a dollar.
The US Government wants to get more $1 coins into circulation. I don't see why they don't just work out some kind of deal with the vending machine companies to allow payments of up to $20 and have the machine dispense $1 coins in change. The Stamp machines at the post office will do that. The hardware to accept the larger bills and dispense the $1 coins is already in use, it's just a matter of getting existing vending machines updated.