What if the bag was in the hold and it catches fire while the aircraft is halfway over the Pacific?
ETOPS aircraft are required to have fire suppression systems to cover the longest potential diversion.
Fire from a single laptop or camera battery is unlikely to overwhelm the cargo fire suppression system.
The concern is more about commercial cargo, e.g., a pallet containing 128 laptops; a bulk shipment of 5,000 lithium battery cells, etc.