Passing Lanes

I went on a day trip today,2 hours 30 minutes down and 2 hours 15 minutes back,no idea why the 15 minute difference as it was the exact same route both ways. I don't spend near the time on the road that I used to but some things never change. Am I the only one that has ever noticed that when you are driving on 2 lane roads and you come to a passing lane that everyone is pedal to the metal,but the second they are back to 2 lanes they are under the speed limit. I drive at least the speed limit regardless of how many lanes are available and have often wondered what causes the rest of the pack to slow down once the lanes go back to 2...is it a competitive thing when there are 4 lanes? Or do people think that they have to be more cautious when there are 2 lanes? As far as the wildlife factor goes it is an equal gamble whether 2 lanes or 4 or even more,they don't consider that when they decide they want to cross the road,and it is the driver that has to watch for the critters,regardless of how many lanes are available. I didn't really intend to write a blog today,but I had to settle my mind over this dilema,it has puzzled me for many years.