This picture was taken with a tripod. Reasons you would use a tripod is when you might want a still, full body picture and if your alone and want a nice still full body picture you can use a self timer and snap a photo of yourself.
this photo was taken in the slot of a vending machine. of course a person cannot fit in the slot of a vending machine so you would use the self timer on the camera. other times you would use the self timer is when the camera can be in a high up place or a really low place like this picture or a corner or difficult angle.