The answers you seek has been already answered but I still think that most people who aquare bitcoin on early stage has no idea what they have in there wallet probably no boody has told them about bitcoin after they might have kept it in there wallet. Some lost the device which was use to aquare the bitcoin and if you Lost your mobile phone which was used to store your bitcoin probably you have lost access to it.
Many people who received there bitcoin never knew the word " Not your key not your coin" they never knew private key was a root access to their bitcoin. Many are Dead just like others have already said.