I'm sure a lot of it is down to awareness and the inability to think for others.
Many drivers just are not aware of what is going on around them... How many times have you come up behind a guy in lane 3, and hasn't pulled over, because he just never looks in his mirrors ? Since I've had the new car my Xenon headlamps work wonders for people like this
It's also quite clear that most drivers don't think of others. If I have a car coming up behind me at pace, I indicate left and move over as soon as I can. I'd rather he be out of my way than be agitated sitting behind me.
There is a game on the M25 called "leave the space", because anytime you leave anywhere near a safe distance between you and the car in front, somebody jumps in from the left and takes up your safety zone
It's down to others just not giving a **** about anybody else, that's all it is.
Standards are very poor, but even worse in many countries ! Mind you, motorway driving in Germany is actually a pleasure
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