I don't know if it actually starts with hair, but yes it's often said that area of interest moves from chest to lower torso to legs as one ages. Is this not widely known or told? Not something openly discussed in public but I thought it's something you hear from across a room and later observe in life.

Never heard this one before..

There may be something to that. We certainly slump more with age, shifting the first thing you're oriented to notice about someone (their face) down to their feet.