Just for the simple fact that most retail clerks here in the US don't look very carefully at the money you're handing them. Due to the exchange rate, it's comparable to getting 5-10 cents off a 25 cent purchase. I don't really go out of my way to get quarters (it's not like I go to a bank and ask for a roll of quarters), but I will ask for quarters in my change when I buy the Tim Horton's donut