Yes this has been discussed before. Apparently Tesla felt they were unnecessary. And I agree. The seat be,t/shoulder belt will hold you in place even during a Ludicrous Mode launch. [emoji3]
The car had handles that didn't attach to the ceiling? Strange. I can't say I've had the headliner off many vehicles, but the few I have had the handles mounted to the roof bracing, not the headliner. Curtain bags were in the B pillar in one, and above the B pillar between the handles in the other.The ones along the top can become missiles if the side curtain air bags go off. A coworker had this happen. Fortunately, his kids weren't in the bac or it would have been ugly. It did bust the window on the other side.