Lines are needed during any spacewalk. In the frictionless environment up there, the only thing to push off against is the spaceship. There is nothing to push back against to get back to the spaceship. Thus, the line is the only thing that will get you where you want to go. What if it breaks?
Newton’s Third Law of Motion states that for every action there is an equal and opposite reaction. Indeed, in frictionless space this is how the spaceship moves. It energetically throws mass out it’s rear.
If the spacewalker has say a wrench, she has a back up for the line. She can throw the wrench away from the ship and back towards safety. But what if she has nothing to throw?
If only the astronaut could somehow inhale inside the suit and exhale outside it. The exhale would nicely propel her. Being able to breathe and spit at the same time would be nice, too.
How about making the suit such that the urethra was exposed to the vacuum? Imagine peeing your way back home to the spaceship. Unfortunately, you wouldn’t be able to see where you’re going easily.
Which leads directly to another available orifice on the astronaut’s body. You could design a suit such that you could fart your way back to the ship. And if you really have a lot of momentum in the wrong direction, there’s nothing like explosive diarrhea to bring you safely back to base.
Laugh at all this as much as you want. But mark my words, if we develop spacesuits that allow such actions, one day an astronaut’s life will be saved because of it.