It sounds you might have misunderstood what these terms mean. People even in a coma 'engage' in multiple activities, such as consuming oxygen, producing carbon

It sounds you might have misunderstood what these terms mean. People even in a coma 'engage' in multiple activities, such as consuming oxygen, producing carbon dioxide, etc... And if they are in a hospital, they are taking up a bed and floor space that cannot be used for another patient, that needs to be actively heated/cooled/ventilated and so on. Their body would literally be engaging with the hospital HVAC systems, especially with 'smart' sensors nowadays that react to room occupants. Even in a purely financial sense, just because someone is physically incapable of opening their wallet or consenting to a transaction, doesn't mean they can't incur debts, or that other entities aren't acting on their behalf.