No. They really don't. You can shove airbags in anywhere and the passenger cabin is not a crumple zone and is supposed to be rigid. The reduction in interior space comes from fatter structure in the pillars and the various other reinforcements (for that cabin rigidity). Then you add fatter interior trim (to hide fat wiring harnesses and reinforcements and thick sound deadening while still providing clean-ish lines) and the effect compounds.
No. They really don't. You can shove airbags in anywhere and the passenger cabin is not a crumple zone and is supposed to be rigid. The reduction in interior space comes from fatter structure in the pillars and the various other reinforcements (for that cabin rigidity). Then you add fatter interior trim (to hide fat wiring harnesses and reinforcements and thick sound deadening while still providing clean-ish lines) and the effect compounds.