You know, it's less of an appeal to tradition-- saying "psionicists existed in 2e, 3e, and 4e, so they should exist in 5e"-- as it is an appeal to continuity: "my psionic character existed in 2e, or 3e, or 4e, and so I should be able to keep playing him in 5e".
And that seems to be a recurring problem with WotC and many of their fans: they don't understand why anyone would ever want to continue their old campaign with their old characters in the new edition, and they don't understand that most players of most games consider this the default assumption of the edition cycle.
And that seems to be a recurring problem with WotC and many of their fans: they don't understand why anyone would ever want to continue their old campaign with their old characters in the new edition, and they don't understand that most players of most games consider this the default assumption of the edition cycle.