What Makes Portraiture Uncomfortable For the Model?

I can never understand why people are so embarrassed about having their photo taken. I mean, we spend a good proportion of our day looking into mirrors. Even shop window reflections are a source of brief, but focussed, imagery. We seem to enjoy it. We like our own image.

Why then do people dislike formal portraiture so much? After all, they have often elected to take part in the process and they have, most likely, made themselves up to look the best possible including clothes and make-up. And, what can be better than having a permanent reminder of just how lovely they do look? It beats all those passing glimpses in car mirrors and other shiny reflective surfaces.

Perhaps it