Good question. Today in one of my classes we discussed attention spans and memory. Interestingly enough, I incorrectly thought people's attention span had been diminished with the introduction of technology. Apparently attention spans are the same, but the amount of stimulus vying for our attention has increased, making it easier to get distracted. The other thing I was misguided on was our ability to store up to 7 items in our short term memory. In the past twenty years the average number of items we can store has declined to about 4. Perhaps drivers are just too distracted from the same stimulus you experienced and have trouble remembering all of the steps to driving carefully? Or, you know, they could just be inconsiderate of others.