It seems more intuitive that Archived category is for conversations that have run their course but which one wishes to store long-term instead of delete, hence the name Archive. Whereas 'All Mail' seems most useful when sorting through and reading through conversations that are still active and ongoing.

Different people differ on this, so it would be a fair compromise if there was a toggle-able option for the use to choose whether to Show or Hide e-mails that are marked as Archived within the 'All Mail' view.