Push Button LED

In the Push Button LED tutorial, why is the blue leg needed (pic 1)? Why not just out from power through switch, led, resistor, back to ground (pic 2 from a non-arduino setup)?

C30806C5-130D-4452-AE62-16B3B115B35C.png

Why not just out from power through switch, led, resistor, back to ground (pic 2 from a non-arduino setup)?

Why not indeed.