Looking at safe following distance a different way...
This discussion should start with the question "what does a *safe* following distance mean?".
A safe following distance means that there is almost nothing the driver in front of you could do to cause you to collide with them.
So let's run the scenario: You're driving along 60 mph, 2 seconds behind another vehicle. 60mph = 88 feet per second, so this is 176 feet. *some* driving schools consider this to be the absolute minimum safe following distance - most of them will say 3 or 4 seconds.
*Something* happens that causes the driver in front of you to emergency brake - my first question: What happens if your response takes 2 seconds (IE you begin emergency braking 2 seconds after the vehicle in front of you).
In this case, since you both were going the same speed, and your response took 2 seconds, if both vehicles have the same braking capability, then you will stop *exactly where the car in front of you stops* (you will collide with them).
At this point, most people will say "my reaction time is much better than 2 seconds - it's nearly instantaneous". The best answer to that is that yes, if you're anticipating having to brake quickly, you can get reaction times better than 2 seconds - but the reality of driving is that this is well studied and understood. The NHTSA investigates crashes, and the average reaction time for all motorists in these situations is around 1.5 seconds.
All things being equal, a 2 second following distance will on average mean you can use emergency braking to *just barely* avoid crashing into the vehicle in front of you if they should suddenly brake hard - but there would be no room for error - and if (for example) the lead vehicle had better braking than yours, that could make it impossible for you to stop without hitting them.
There was a time when driving schools taught calculations based on "carlengths" - which is really redicilous. Over the years, I've occasionally asked students to estimate distance using carlengths, and almost no one can do this with any useful degree of accuracy. Measuring by time adjusts the distance automatically, whereas measuring by "car lengths per 10 mph (or whatever) is somewhat complex, and most people who claim to do this likely don't bother".
My experienced reality is that most people either have no awareness of safe following distance, or they simply want to crash. I don't think I've driven anywhere in the US and not been tailgated multiple times.
Even law enforcement seems to be ignorant (in general) about following distance (which is probably why most people don't seem to maintain a safe distance). Statistically, about 1% of tickets are written for FTC (most often after a crash), whereas around 25% of tickets are written for speed.