I guessed that was probably the case with charities.
One site I read said that although the regulations should apply to all furniture sold, trading standards had very little power to act against a private individual which is why they are omitted.
Personally I can see no ethical problem selling most things, PROVIDE you are honest and disclose any relevant details. As I said, some one may wish to buy it to re-upholster, it would be a shame to dump a perfectly good frame. This would be similar to cutting the plug off an electrical appliance. The new user is them responsible for re-wiring and if they wish getting it PAT tested.
DJ, I looked at the fire stats as you mentioned. By far the biggest cause (about 80% in 2013/14) of accidental home fires (you might be surprised by the number of deliberate ones) is electrical appliances and wiring, about 80% . How many of us have our appliances and wiring checked regularly. We had ours check and certified a few years ago, but that was the first time ever by a professional.
Electrical connections do deteriorate with time, joints relax, and can overheat. Our daughters house which was about 10 years old was lethal, mainly loose connections in socket and light fittings, easily fixed but had they been left could have caused a fire.