You apparently didn't live through the "National Maxinum Speed Law" time period (where the entire country was 55 mph).
We live in different worlds. I pass way more people than people pass me. There's not a speed limit over 55 mph in my entire county. If I don't stray far from home on a tank of gas, most of that tank will be about 60 mph or under. Do I go 65 mph in a 55 zone sometimes? Sure I do, but my average would be more like 60 mph. I might see a handful of vehicles on the road when going to work or coming home (about a 12 mile drive one-way).
A traffic jam would be some farmer's cow on the road! :)
I almost had my first accident with a student driver this week. She wasn't the most experienced driver (meaning her parents haven't driven with her at all yet). This event wasn't her fault, however. We were going over a large hill, and she probably let the car slow down a bit (maybe 50 mph or so). I'm sure that annoyed the two vehicles behind her, & they were really on our tail. As we came over the hill, we both spotted a young dog (half grown Golden Retriever in my opinion). The dog was on the left shoulder, & when it saw us it bolted right in front of us. We both slammed the dual brakes quite hard, and cars behind us had to swerve to miss us! We missed the dogs and the trailing cars missed us thankfully! If it had been a deer, I may have let her take it out. Killing a dog is another story! It would have freaked her out, too! So far my only road kill with a student driver has been an opossum. She hit it quite well (double thump), but they are sort of ugly (no disrespect to God's creatures however). That was about 10 years ago.
Back on topic -
I'm pretty much in the 40-50 mpg range most of the year with my Mirage. The exception would be consecutive days of -20F or lower. Then I might see the upper 30's, especially if I let the car idle a bit to warm up. If I had to drive 70+ mph most of the time & use A/C more often, I would probably own something else. A Mirage feels more like a slow tin can in heavy traffic city areas to me.