Why are people so stupid?

I took some time this afternoon and went for a ride. It's the first ride where I really feel like I am over being sick. Thank goodness. I felt like I messed up my eating or someting before I went on the ride, or maybe it's just that I'm totally out of shape. I did my standard "from home" ride, with some extra exploring of some side roads.
Ride description: From my house I went west with a tailwind onto Depot road. The wind rarely comes from the east, so this was strange and I was moving along at 20+ with little effort. I turned onto Meadowvale and instead of taking Fredrick to Gardner to 146, I stayed on Meadowvale to Altamont road. Lots of climbing on Meadowvale. Short bursts great for a workout. After those little climbs I felt confident so I went the hard way up Berne-Altamont road instead of the "easy" way up Township. I felt good, but would say I "bonked" halfway through. I felt so good up that beginning steep stretch. I was standing, using my legs and felt like I could do it all day, but after I sat down when it shallowed out I couldn't get back up again. Then my stomach started to roll and I felt a little shaky. I climbed the rest and enjoyed the ride at an easy pace after that until Carmel called and was stressed that I wouldn't be home in time.
I was at Thatcher (8 miles from home) and felt pressure to move it along. Easy because I was at the top of the hill. I felt stronger than I had through the ride doing the momentum uphills through the park, then hit the big downhill. I hit 40 MPH and moved out to the center of the lane, tucked in and hit 45. Two cars decided to pass me by going over the other lane, then promptly pulled back into the lane and put on the brakes to get down to the speed limit and forcing me to use the brakes. Very frustrating. I'm sure I could have hit 50 MPH. Why do people drive so stupid?