Not needed at all, Endmaster for instance does all his stories without any of that.
I still think they're worthwhile to learn as they do let you add some neat options (such as delayed consequences to certain choices), and basically as soon as you understand IF/THEN/ELSE logic and that a variable is just like a box that stores a number, you can handle most scenarios you can think of.
But the major elements most readers are still interested in here are writing quality and branching. Scripting can add some nice touches and sense of polish to that, but it won't save a story that doesn't work on its own as a story.
