That's a habituation to the reality of the Win32 style — "Find reached the end of the document | OK"
Users don't have an a priori instinct to dismiss dialog boxes out of spite — on the contrary, the elderly noob reads every one carefully as if the wrong choice would actually destroy the chair beneath them. A new dialog box like that would ruin their day, and mine when I get their panicked phone call now that they've gone off script. If they ever do build a mental model of the UI, they'll have learned otherwise.
But because of the way UI is designed, one of the first elements of the UI mental model your elderly noob will learn is that dialog boxes are to be ignored.
Users don't have an a priori instinct to dismiss dialog boxes out of spite — on the contrary, the elderly noob reads every one carefully as if the wrong choice would actually destroy the chair beneath them. A new dialog box like that would ruin their day, and mine when I get their panicked phone call now that they've gone off script. If they ever do build a mental model of the UI, they'll have learned otherwise.