Life gets busy. Between my job and Saturday courses, I'm pretty much working a six day week. I do a lot of driving, so I'm topping up the tank every other day sometimes. I keep all of my receipts, record the mileage, stuff them in the glove box, intending to update Fuelly...but once in a while I forgot my pen and couldn't record the mileage on the receipt, so I took a picture. then it's the end of the month, I look at all those receipts and think, this is too much like work to find out I'm getting the same average fuel economy. Laziness kicks in, then when the pump at Costco asks me if I want a receipt, I start to just click "No" because it means I can just hang up the pump, get in the car, and beat the guy who's selected a receipt to the exit.