Great portraits give you a personal, more intimate connection with the subject. And while I agree, I also know a performance is often just that, a performance.
Great portraits, great photographs for that matter, enable the viewer. They let you to do something you normally cannot or would not do.
Seeking truthfulness, is risk-filled. So we stare, interpret, and stare some more. But staring is not polite. Unless of course, you’re staring at a photograph.