I know that larger cars need stronger A-pillars because the A-pillar is supposed to keep the cabin from getting smushed in a roll-over, and so the A-pillar needs to have a larger cross section.

But why don't they get that increased cross section by extending the A-pillar in the directions toward and away from the driver and keep its size perpendicular to that the same? That should give a stronger A-pillar without changing how much it blocks. It would slightly reduce the interior volume of the cabin bit that would come from space that normally isn't used.