We've ben over this a gazillion times on here but once more won't hurt I guess. I understand your diagram 100%. However, from a car driver's perspective, he wants to give the same space between his nearside and the thing he is overtaking. In riding two abreast that thing he is overtaking is closer to the middle of the road and thus he has to go on the far side of the road more than would otherwise be the case.
I understand that cyclists want the car driver to overtake single file just as he would overtake two abreast, like your diagram, but that just isn't the case.
So the car driver perceives that, in riding two abreast, cyclists are forcing him to either sit behind or attempt an overtake which would be more dangerous for him than if they were riding single file. Cyclists can argue until they are blue in the face but that particular perception is reality