A man who lives on the tenth floor takes the elevator down to the first floor every morning and goes to work. In the evening, when he comes back, on a rainy day, or if there are other people in the elevator, he goes to his floor directly. Otherwise, he goes to the seventh floor and walks up three flights of stairs to his apartment. Why?
His height has to do with it...
The man is short of stature. He can't reach the upper elevator buttons, but he can push on it with his umbrella on a rainy day.