Simple fact is we all follow the same rules. Causing other traffic to brake or divert course during a manoeuvre is not on.
Arguing the roads are too busy to achieve that doesn't cut it either, as that's all the more reason to keep left.
It's utterly self centred behaviour generally speaking, often forcing traffic from lane 2 into lane 3 as well.
Personally I couldn't face the embarrassment of blocking lane 2 of the m4 for miles on end, causing three lanes to back up, with so obviously nothing in front. It just defys belief for me.
Having said that, most Laurie drivers appear to be much better add judging cars slip road entry speed than the car drivers themselves. Often dropping back to let traffic on.
Those two sides of the same pigeon hole are clues, IMO, that show up the impatient moron with a big bad truck behind him, and a more experienced driver.
Tanker drivers seem to be far more "professional" for obvious reasons, and have an almost invisible presence in the road. (Apart from the over officious tit that insists on delivering at my nearest lpg filling station causing the pumps to go off, just as I arrive with no gas ....not once but twice)