Why Does Everyone Speed So Much on the Interstate?

Where I live, our interstates are mostly 70 mph. All my life, I’ve driven 5 over, so I typically set my cruise to 75 mph on the interstate. I’ve never been pulled over for it either.

However, if there’s one thing I’ve noticed that’s so frustrating is how even going 5 mph over is still slow. Everyone else zooms past me going at least 80-85 mph, if not faster. I always feel like the slow one. Why is it that everywhere else, people seem to drive the speed limit (city roads), but somehow they feel safe and okay speeding so much on the interstate? I mean there is still a speed limit after all…