The takeoff would always be at 90 degrees to the land, which is full of obstacles and people. The departing machine didn't really have a choice.
While climbing out, the landing aircraft was in a blind vision spot above the roof and centre window divider, and the landing aircraft had the departing acft in his blind spot behind the A pillar. Only radio calls would have alerted them, or the efforts by the concerned pax. If he had tapped the left shoulder, a different result may have ensued, but he couldn't reach that far. And it may have been too late.
There is always a lot of cockpit distraction with joyride pax, squealing, pointing, waving cameras, and asking the pilot questions if they are on intercom. Easy to blot out a radio call.