Comment 6 for bug 895172

What makes them different is the direct exposure to the impact.
If you have a Carryall carrying a Demolition Truck, and the Carryall crashes, you are directly ramming the Demo Truck into the ground out of hundreds of leptons height.
If a Nighthawk crashes, it's the Nighthawk only who impacts the ground, the passengers only ever interact with the Nighthawk's insides.

To put it differently: While a passenger inside another unit still dies, he is largely protected from damage - as evidenced by the fact that shooting a Nighthawk down to 50% doesn't mean the passengers are damaged as well. So I find it perfectly reasonable to say they sustained enough damage to die (e.g. broken neck), but they were protected enough to not have their death weapons triggered.

In addition, you also have to consider the effects on balance: While the opportunities for abuse in the stock game may be few, the fact stands that triggering the death weapons for passengers would turn Nighthawks full of Terrorists into nigh unstoppable Cruise Missiles: In a bad scenario, you shoot down a Nighthawk, two Terrorists chute out and sail down as parabombs, while the Nighthawk rams into your refinery and destroys it with the power of three Terrorist-bombs.
No matter what you'd do, you'd be screwed: Don't touch it, it lands in your base and the terrorists escape. Shoot it down and everyone escapes: You've got living parabombs/escapees. Shoot it down and no one escapes: You've got a quintuple-power kamikaze-Nighthawk.

Players should have a reasonable chance to successfully stop an incoming passenger aircraft. There's no success if you're getting screwed either way.