Consumer Confidential: Mnuchin's wife isn't the only one defining herself through the brands she promotes

Treasury Secretary Steven T. Mnuchin's wife, Louise Linton, did herself no favors when she took to Instagram last week to brag about the luxury brands she was wearing, and then belittled a commenter who called her out for her let-them-eat-cake behavior.

"It's as stupid as stupid gets," said Leslie Goldgehn, a professor of marketing at the University of California, San Francisco.

But I'm not here to join the chorus of critics who have made Linton the poster girl for crass, tone-deaf displays of wealth and thoughtlessness. I have another question in mind.

Why do people do this?

I don't mean why people behave