I wonder if you’re not seeing flight attendants? I live in a neighborhood popular with cabin crews, as I am near 2 major NYC airports and the JetBlue headquarters. They are usually going around in a dress coat over their uniform, groomed & you really can;t tell they’re wearing a uniform under the coat – and they always have their wheelie bags with them. A lot of times, in cities other than their home city, they just have a “crashpad” which is basically an apartment loads of flight attendants share hotbunk fashion because each is only there 4 days of every month. If you see certain people regularly but not daily, that would be my guess. Look for employee ID tags on the luggage.
But flight attendants don’t carry those HUGE wheelies that you could stuff Dick Cheney in, so I dunno.