Answer:
When the economy was good people were just saving the coins and not spending. Now that the economy is worse, there should be more coins circulating.
It also depends were you are. While the quarters circulate in the entire country, the area around the state gets more of them than any other part of the country. The first 13 states were (mainly) in the north east, so that is where they have been the most common. They are now starting to move south - they've already done Tennessee and Louisianan is this year.
In the coming years they will move west and the coins will become more rare here in the east.