Self-protection. There is no logic in this situation. You are an innocent person...treated as if you were a potential plane bomber and baby killer.
Your lipstick is viewed as a deadly weapon.
Your shoes could hide bombs.
Your scarf could be hiding something (why else be asked to remove it).
Your bag could have a bomb in it. So they yell at you, 'move on', 'remove your shoes', and 'put your bags in the bin', 'step back' or 'step forward'.
Your jewelry could be a bomb so they paw through your personal belongings, bare hands, through your toiletries and toothbrush.
Everyone deals with this in their own way. One friend 'goes catatonic' until through 'security'. Another well-traveled friend says she 'goes on auto pilot' and another, who travels often, wears ear-plugs and goes through the motion, like a robot, she says. 'You can't be thinking about it'...said another chum.
Travel...is still worth it. Security is grubby.
The destination is the thing. I love to fly. Even so...