[lefra]

People merging have right of way only on the parisian périphérique. On all other motorways in France, the merging cars must yield.

It is common courtesy to move over or match speed so they can merge more easily, but that's not the law.

[imp0cat]

Interestingly, I believe this manoeuvre (move over to make room for cars entering the highway) is banned in Germany, because it can cause accidents as the cars from the slower right lanes suddenly move to the left lanes.

[ahartmetz]

That is not correct - making room is legal and encouraged. You are free to use left lanes for good reasons - being too lazy to switch lanes is the one common not good reason.

High speed driving requires looking far ahead to anticipate lane changes of other drivers.