This is all very well but don't forget you paid your insurance premium in good faith (most likely provided an estimated value as well) only to have the insurance company play games with you when you had the misfortune to request the service you were paying for.
When people have such a severe accident that a write-off occurs its most likely an emotional time and also a lot of inconvenience, therefore once an offer is made I suspect most customers accept it. I'm sure the insurance companies have a wealth of data that shows that this practice works and saves them lots of money, hence why they keep doing it.
In my own case it took me nearly five months to receive a fair offer, only after referring to the Ombudsman, and all that time my car was in limbo.
Never again, hence why my P&J is now covered on an agreed value policy.