Strike One: Most of the time, there will be a human head in the way of this code. So right off the bat either you're asking a viewer to move another human's cranium out of the way to catch the QR code, or they simply won't see it because it's obstructed.
Strike Two: This particular code was found on a subway line that is never above ground to pick up a signal. Amazing.
Strike Three: Honestly just what the balls.
Now, some trains get moved from line to line, but even then, a QR code on a subway of any kind is insane and bad and what and no. Please, badvertisers, stop this.