Riddles: Elevator

There was a man who lived in a 14 story building. He went to work everyday and pressed the button for the lobby in the elevator. When he came home everyday he pressed the 7th floor button and then climbed the stairs from the 7th floor to the 14th, unless somebody was in the elevator with him. Why didn't he ride the elevator up to his floor?

A. He was a dwarf, and could only reach the button for the 7th floor in the elevator.