Why even sell a physical box if it has absolutely no benefit over a digital download? I wonder if it's at all driven by desire to trick people who want a physical disk copy (ie, a copy that can be resold or traded)?

Given that people generally expect physical copies to have a disk (at least for console games), it feels like false advertising.

Having a product on a shelf is a form of marketing. It's why big releases get a full wall at GameStop. They cna keep a box in the back, but the publisher has paid for all of that shelf space, and they've paid for it because it makes it look like a big deal to people who are just wandering in looking for a gift, or for their next thing to play between Fifa or Madden releases.