Because the average American has no CLUE how much money a Billion dollars is. It's just a number tossed around in the news, and the numbers they hear coming out of the Government becomes even larger and larger. This was a very effective way to show just how much money is in a Billion dollars. Americans know aircraft carriers are huge, so now they can see just how huge a stack of one billions dollars actually is. I also like their newer commercial showing a tired guy placing $500 on every seat in a football stadium, while the announcer tells them that a Billion dollars would equal placing $500 on every seat in EVERY professional football stadium in the country.
Our Gov't just passes a TRILLION dollar budget for this year alone. Google just how big a stack of one trillion dollar bills is. It will amaze you!