Social Security Administration. The Social Security Administration assigns social security numbers; administers the retirement, survivors, and disability insurance programs known as Social Security; and administers the Supplemental Security Income program for the aged, blind, and disabled. SSA.
Prosopagnosia is a neurological disorder characterized by the inability to recognize faces. Prosopagnosia is also known as face blindness or facial agnosia.
All this brings more attention to the fact that Sia isn't showing her face, likely making viewers more curious about what that face looks like. If you're looking to divert attention from the specificities of your visage, it's probably best not to draw attention to the fact that you choose never to show it.