I agree. I was a member of the Institute of Advanced Motorists and was an observer for our local group helping other drivers raise their driving standards to pass the test.
We were also very hot on courtesy and even hotter on anticipation and avoidance of potential problems, all the while whilst "making progress" ourselves. Part of that was providing space for other drivers joining a dual carriageway or motorway, either by speeding up/slowing down ourselves to create a gap in our lane, or moving lane ourselves. The rationale was that as long as it didn't hinder us or anyone else, then why not do it to help someone else. We'd not move over lane if it would cause another vehicle to change course (speed or lane), but if we could do it safely and not affecting anyone else, then we would. In fact, general advice was to move over at the approach to the exit slip road on the grounds that there would likely be an entry slip road quarter of a mile further on. Easy enough to move back left again if no vehicles entering. ALL in knowledge and observation of other vehicles - we certainly wouldn't be barging over if there was someone already there or a faster car approaching from behind who'd need to move over themselves if we got in their way.
We had it indoctrinated into us that whilst we needed to know our "rights" and be assertive to avoid confusion etc., at the same time, we were responsible, like all drivers, to avoid putting other drivers in harm's way if there was something we could do to reduce risks/hazards ourselves.
Part of the IAM test was a commentary where we had to describe the roads, the hazards, and more importantly, our reaction to what we were seeing and why we were doing certain things. Whilst the examiner would instruct us specifically when they wanted us to do the commentary, we could always voluntarily do it ourselves, either for the entire test or for other parts, and we'd encourage our associate members to practice doing that. It gave the ability to explain to the examiner why we were doing things that otherwise didn't appear to be required. Our particular group made a big point of always doing commentaries on motorways and dual carriageways to explain to the examiner why we were moving over if it wasn't obvious, likewise why we were slowing down/speeding up. The examiner himself, who we regularly met, would regularly commend us for taking that stance as he said he was often confused and conflicted when a driver did "strange" things without obvious reasoning and that explaining would often mean a borderline pass/fail would usually become a pass! All borne out of courtesy and avoiding risky situations, regardless of the rights and who'd be at fault!!