A full tax return contains a lot more information than a summary number (“what you earn and the taxes that flow from it”). What benefit are we trying to achiev

A full tax return contains a lot more information than a summary number (“what you earn and the taxes that flow from it”). What benefit are we trying to achieve and how does applying that to most corporations get that? Saying we should have it for publicly traded companies makes a lot more sense than every private company let alone every person.