So why do you try? On a dual carriageway with two lanes in each direction, when you pull out to overtake another lorry you're condemning all of us who were happily driving along at 70mph to sit behind you while the impossibility of your cause sinks into your head. You will receive no co-operation from the lorry you're overtaking, which will continue at 60mph rather than slow down a little to let you in.
Even if the lorry you're overtaking is going slower than you, it's not much better. At 59mph, that means you're a full 1mph faster. In 3,600 seconds, you will travel 1,760 yards further. In other words, your relative speed is about half a yard per second faster. If lorries are 10 yards long and you leave 5-yard gap between each other, that means it'll take you a minute to creep the total of 30 yards you need to go. You will reach the end of a 300-mile journey a full 5 minutes sooner than if you'd been stuck behind the other lorry the whole time.
Meanwhile, you've added about 17 seconds to the journey times of each of the 50 people you've been holding up, because that's how much you lose when you drive at 60mph for minute when you could be driving at 70mph.
I know you don't have to be good at arithmetic to be a lorry driver, but I'd have hoped that being bad at it wasn't condition of receiving a Heavy Goods Vehicle licence.