Having concluded principal photography in Atlanta, Georgia, Spider-Man: Homecoming has been shooting in New York over the last several days, and one Redditor posted a set picture supposedly showing flyers advertising a new Stark Expo that will happen from October 17-27, 2018 in New York City.
If this photo was indeed taken on the Spider-Man: Homecoming set, then that would provide enough reason for why Tony Stark is in Peter Parker’s neck of the woods, as the Avengers are no longer based in Stark Tower post-Avengers: Age of Ultron.
That said, it’s unclear whether the Stark Expo is actually happening during Spider-Man: Homecoming (thus placing the movie one year ahead of when it’s released) or if it’s being advertised a year ahead of time.
Either way, while he’s involved with that, he can also take the opportunity to meet with Peter again.