I suspect this happens less often than people think. Most elephant races are up hills and are at speeds significantly under the demonstrated maximum of the truck on level ground. I routinely get passed by tractor/trailers when I'm doing 65mph in the right lane of the freeway with my travel trailer. Even a slight incline and I end up blowing right past them.
My guess is that two fully loaded trucks just have a similar maximum speed in a given power-limited situation, and when combined with the natural desire to not give up even 1 mph of hard-won kinetic energy, we end up with elephant races.
depends what you think is "less often than people think", plus you need to put it in country context.
In Poland it is a real problem. On the distance o 100 km (60 miles) it can happen 3-4 times. If you travel for 300 km it means you will be swearing 10 times when stuck in a line after some lorry.
Also the speed difference is much higher on Polish highways because cars can legally go as fast as 140kph while upper limit for trucks is 90kph. This is a huge difference, lots of brakes to burn before you slow down to match that speed.
If elephant racing very occasionally prevents an accident due to slower speeds, it might benefit all road users as they don't have to pull over for emergency vehicles, and don't have to wait for debris to clear.
I feel that this is something people didn't have to do so much: with an analogue speedo, you can't really see your speed to 2 sig figs while driving, with a digital one, you know if you're at 20 or 23 (after your car speedo error, obviously). The implication is that it previously wasn't so important to drivers.
It's not that simple. According to [1] the relationship is U-shaped, with the least accidents per million miles driven occurring at about 1500 vehicles per hour. Less traffic increased accidents number, more traffic decreased accidents number but increased average number of cars in each accident. The sweet spot was in the middle.
Additionally after a certain traffic threshold accidents stop being deadly (because of slow speed).
But the results varied depending on road types, countries, time resolution of data and weather conditions.
Also minimal safe distance is 3 seconds at your current speed. If you can't keep that distance because of traffic - you should slow way down, not to 60 km/h but much lower. So either your comparison isn't fair or the person doing 60 km/h with 2 seconds of gap is the reason the road is unsafe, not the traffic.
And if you've ever actually encountered a queue behind a slow vehicle, you'll know that leaving too much of a gap will cause undertaking luxury German cars to magnetically be sucked into it (no fault if their drivers of course, its all done in the engine control software I hear), suddenly leaving you with 1 second of gap, until you can ease off and grow the gap gently without having the car behind you pile into your rear end.
Either way, the separation in free traffic is hugely greater than in any queue.
A similar case, more frequent case here in a touristic place with single-lane routes is lines of vehicles right after each other, that don't know how to overtake the one before, but neither leave space in between so someone else _can_ overtake them.
In a complicated mountain road, I _may_ be able to overtake a truck once in a while (depending on incoming traffic, turns, and going uphill/downhill) - but the effort required to overtake 2, 3 or more vehicles at a time is almost impossible.
In France, at least, when there are more than two lanes, basically no one drives on the rightmost lane.
Yes, I know about the traffic law requiring staying in your lane if there is dense traffic. I'm specifically talking about the case when there is little to no traffic.
It's actually been illegal for some years and can get you a £100 fine, though I don't know if that's ever actually happened: you'd have to have the bad luck to encounter traffic police who do anything other than speed-gun free-flowing motorways from bridges.
It doesn't matter what you're driving, if you're getting into a flow that's going faster than you are you are either going to force it to slow down or cause a crash, depending on how much space is in front of whoever you choose to cut off.
I'll generally cut the trucks some slack because it's not like they can gain 10-15mph at the drop of a hat but when car drivers do it it's impolite and amounts to a big middle finger to everyone else.
Say a truck has a length of 16m, and starts the overtake 10m behind another one, and merges back in 10m in front. So that's an overtake distance of 36m. At 1mph relative speed, this takes 80 seconds.
Meanwhile, the cars behind the truck have all had to drop out of cruise and are now doing 10mph under their preferred speed (car speed limit is 70, lorries are 60). So that 80 seconds and 10mph under is 10 seconds of overall journey time. Not enormous, but it multiplies across all the cars in the queue, and across the number of lorries making this move in a journey.
However, the point is that if the overtaken lorry could just ease off the throttle by a single mph, he'd halve the overtake time, at a cost to himself of 1mph less for 40 seconds, which is less than a second of journey time.
So, when overtaken, a very minor "altruistic" gesture on the part of the shower lorry pays back dozens or hundreds of times over to other road users. And that's without considering the travelling waves that linger after dozens of cars slow down from a rolling roadblock and can make the whole road slower for everyone for a long time.