looks wack. this is the sexiest thread, not the "most pragmatic' thread. But seriously, it's a DH bike, the BB probably gets low AF deeper into the travel, and the weight gain is hardly an issue on something you're not pedalling up things.
They're riding on super groomed moto jumps. There's no rock gardens to jostle their chain off, or rocks/logs to bash their chainrings on. Even if they dropped their chain, they probably don't need to pedal unless they beef the landing of the previous jump and lose their speed.