Contractions are handy little language shortcuts we all use dozens of times a day. We would find it a little strange if we suddenly could not use couldn’t, won’t, isn’t or didn’t.
In the book I’m writing the characters are like us in many ways and unlike us in others. I want the girls, as they age, to talk like human girls talk. They are pre-technological girls, though, so they won’t LOL. Neither will they say “won’t.”
I wanted to signal some slight difference in their language; just a little reminder to the reader that they are not after all human. I could sprinkle their talk with invented colloquialisms. I will probably do that a time or two, but a little goes a long way. I chose, instead, to avoid contractions. The narrator is allowed to use them, but the anjels are not.
I may keep myself in this little box, or I may get tired of it and break out. I’m too close to the novel at this point to worry about making that decision. I’ll wait to see how crazy it drives an editor.