I thought about the propane angle. But propane lasts a lot longet than a battery charge, a propane tank doesnt degrade like a battery does, and a battery is more expensive than a propane tank (both construction and recycling).
So, its higher cost of entry, potentially high cost of “recertifying” (ie turning around an empty battery into a full one).
It seemed more likely that both the user and the company to get screwed over by duff batteries and surprise costs