A resident of a high-rise has a peculiar habit. He lives on the 18th floor. When he arrives in the elevator at his building to go home, he presses the button for the 10th floor, gets off and walks the last eight flights up home. When leaving his unit, he gets in the elevator on the 18th floor, presses the button for the lobby and goes on his way.
He does this each and every day.
What is the reason?