Moving over for slip roads- why don't people do it?

[MGF]

I prefer to accept that the fact we have priorities on the road necessitates those having to cede priority being adversely affected by those who have priority.

[WhoseGeneration]

I really don't understand why this topic has become so long.
It is very simple, AD is about being flexible in your driving, such that you plan for eventualities, seen and potentially unseen.
Which means thinking about each potential hazard situation and accepting that others might not adhere to the HC, especially, as with this topic, how to join Motorways, or, even, DCs, as this is not part of the test to obtain a licence.
So, do what you have to do, in any situation, to ensure your safety and perhaps of others.

[Silk]

I really don't understand why this topic has become so long.

Probably because I got involved.

[Silk]

I prefer to accept that the fact we have priorities on the road necessitates those having to cede priority being adversely affected by those who have priority.

We're now, due to misplaced courtesy, getting to a situation where drivers are confused as to who has priority or making false assumptions. This is what seems to have happened in the OP's case.

Most of the time, things work perfectly well when people stick to the rules on priorities. On occasions, it's necessary for people to give up priorities for the greater good, such as letting people out of a side turning into a busy road or moving over in order to assist a lane change or motorway join. But, if they contribute nothing other than to give the driver giving up priority a warm glow inside, then it's probably best to leave things as they are. IMO (based on hundreds of thousands of motorway miles driven) of course.

[Ralge]

I really don't understand why this topic has become so long.
It is very simple, AD is about being flexible in your driving, such that you plan for eventualities, seen and potentially unseen.
Which means thinking about each potential hazard situation and accepting that others might not adhere to the HC, especially, as with this topic, how to join Motorways, or, even, DCs, as this is not part of the test to obtain a licence.
So, do what you have to do, in any situation, to ensure your safety and perhaps of others.

And bear in mind that German drivers are taught on motorways prior to their test AND that, with many stretches of Autobahn down to just 2 lanes, they are encouraged to accelerate briskly (but many on-ramps are virtually cork-screw bends with little view until very late of the traffic already on the carriageway) and use the first bit of the hard shoulder if need be. So don't expect the truck or car driver in lane1 to move over.
I sat once with a German driver over here who had put herself into conflict with joining traffic (prior to the UK familiarisation course) by not considering or seeing the need for a move into lane2.
Being alive and alert to others' radically different approaches to the driving task, responding flexibly and looking after your own and others' safety is indeed the key.