Delivering in the city, I learned that some people apparently consider the person who risked life and limb to bring them their cheese rose oolong tea unworthy of even hello. A lot of my deliveries were to fancy new glass towers that looked like the buildings in video games. The twentysomethings inside would barely crack the apartment door enough to take the bag of food, or maybe just mouth “thanks” without interrupting their phone call.

Another unpleasant surprise: For almost two-thirds of my 43 deliveries, I got no tip. You may think the delivery fee takes care of the rider, but the apps’ pay structure leaves riders dependent on tips to make a living wage.

A friend of mine who has been delivering for three years, Wilder Selzer, called the job “a great window into our stratification.” Quite a few times, he said, he has delivered to people — men and women alike — who answered the door in their underwear, but not in a sexy way.

“It goes back to the class thing,” he said. “You’re like a eunuch — it’s O.K. to be naked in front of you because you’re not a person person.”

The cloak of invisibility descended in restaurants, too. I picked up an order of Rasta Pasta at a bar and grill in Bedford-Stuyvesant from a woman who kept her head turned 90 degrees away as she handed me the food, as if it, or I, were a rotten fish.

The class thing, Wilder said, could have a paradoxical effect on tips. People in public housing tipped consistently, he said, while students at N.Y.U., one of the nation’s priciest colleges, rarely did.

In my travels, the only person who gave me the time of day was a young woman in a housing project in Dumbo, Brooklyn, who had ordered a bottle of wine from a liquor store. It was my first alcohol delivery, and we were both surprised to learn that I had to scan her proof of age into my phone. It took me multiple tries and several endless fumbling minutes. “We’re learning together,” she said. “Now I know, too.”