A man rides his elevator from the 13th floor to the 1st floor every morning, in the afternoon after work he returns to the same elevator to ride it back up to his room but only rides it to the 7th floor and walks the rest of the way up. He does this everyday. Why is this?

Exercise,
Superstitious?

He's a midget, can't reach the 13th floor button.

He's a midget. The correct riddle is
" There is a man who lives on the 13th floor. Everyday he comes back from work on afternoons. When the man comes back from work on sunny days he presses the 6th button on the elevator and walks the rest of the way up. When the man comes bak from work on rainy days he presses the 13th button. Why does he do this?