SCENE: A PACKED New York City subway train, headed toward midtown in morning rush hour. Professional women, nearly all scanning smartphones, balance bags on their knees, in the crook of their arms, on their shoulders, or, cringingly, between their shoes on the germy floor. I clock a weathered Goyard purse, a boxy Kate Spade bag, a structured Prada “Saffiano Executive Tote Bag,” a cotton tote printed with the name of an art fair. In them? Judging from conversations I’ve had with dozens of women, the contents could include...