Is the room too cold for them? Do they understand how to control the a/c? Are they blowing smoke out the window? Who knows?
I'd close the window, leave on a/c, or leave window open, turn off a/c AND leave card of minimal instructions for operation of a/c with maximum efficiency and to save energy ... close window when in use ... blah blah blah. I don't know why people do this. I had only a few a/c's and had instructions at the a/c, at the thermostat and on the windows! Yes, I did.
Had a few guests who used all three ... heat, a/c and open window. When they checked out discovered ... Heat set to 68, a/c set to 62, window open.
I've returned to hotel rooms to find that housekeeping has changed the settings on a/c so it's not unheard of for staff to adjust..