I utterly agree although on roads like the m25 by heathrow where you have 5 lanes it gets tricky. If everyone followed the highway code on that stretch in the mornings there would be no space to pull in to the nearside and make you exit. It's already like threading a needle though a gnat's vagina as it is.
Yep, it's sheer weight of traffic that buggers it. Motorways where never designed for that much traffic.
Trouble is, those habits formed in rush hour by a driving population never trained to drive on them are carried on at all other times. So drivers just sit in any lane....although mostly the middle lane.
Sometimes legitimately, in quiet times, for a reason such as Dear leaping from the hard shoulder, such as they do between Jcn 10 and 8/9 on the m4 for example. Or that lane one is so rutted the car won't drive straight and tram lines alarmingly.
But none of that means it's ok to sit in lane 2 or 3 if traffic comes up behind you.
...in fact, if nothing is in the road with you, who cares. Do what you like. Empty motorway nothing around, sit in lane 3 away from the hard shoulder, nobody cares. Until somebody comes up on you of course. Such occasions are very rare on busy motorways these days though, obviously.