The problem isn't batteries carried on one's person. Those can at least be dealt with when they start to misbehave. A little water is usually all it takes.
Not ideal, true, but better than those hundreds of batteries stacked away under the floor, all together in one neatly packed pallet in which will help trigger a chain reaction, where no one can access them, and with a fire fighting system that will do absolutely squat to quell burning lithium...
The killer is in the cargo hold, not in your pocket.