I think we can get tangled up in why the regulations were brought in and also the scope and scale of the problem. if we consider a room is a compartment designed to keep occupants safe then the door, walls and ceiling make up the compartment and these are the structural elements that must last as long as possible, so doors ceiling and plasterboard walls in a new build all 30 minutes protection. Take the same in a twenty-year-old block of flats with concrete walls ceiling etc then the wiring could be in trunking at the high level fixed to the concrete with plastic plugs. Because of the difference in heat, the trunking can start to fail and collapse into the cooler zone below where the occupants are escaping or the fire brigade could still be operating and then entanglement becomes a real issue and a cause of death. Another thing we have found is where the heat (hot air) can travel along trunking and pop off the lid a long way from the fire and stop evacuations due to entanglement this way. Long lengths of steel are liable to collapse from stress and twisting due to heat so likewise, we protect with twin layers of fireboard to give some protection. In a standard house, the risks are much lower than in blocks of flats and commercial buildings because of the different building methods and the numbers of occupants.