A lot of people hold their fear in their arms/hands and in the way they hold and think of their poles. Kids often use them as security.
Really though I see more and more folks without every year. I took my wife's [poles] away and she is doing better than ever! She then took her girlfriends away and the same result. -Jacques
Now try taking one ski away. Let them ski on the other. After half a day give that ski back and have them take the other one off. Don't give that one back till the end of the day. (Don't be tempted to cheat on this process and store one ski away for the day, just changing feet. Do the process of switching- much better drama plus makes them think about it. They might realize what's the difference, why not change feet with the same ski? - learning!)
Next day, repeat the above procedure but start with the opposite ski. Make sure to have a good dinner after skiing.
Day 3: Pretend you are going to take a ski away, (again the opposite one), but allow them to beg to keep both skis on. As a compromise befitting the US Congress, agree to allow them to keep both skis but only if they switch which ski is on which foot. Have them switch immediately.
Now when you ski with them have them tell you what it's like with one ski on each foot. Have them notice what the inside one does and what the outside one does and when etc. Have them tell everything about what they're doing. If they stop talking about what they're doing, tell them you'll have to go back to taking one ski away.
Don't take them on real difficult terrain, let them enjoy skiing! Now they'll start getting better on their own, plus you'll be able to coach them and interact because they are aware of what their feet/skis are doing. They'll get better even faster, you'll be a genius.
Pretty soon you'll be on square 2 and they'll want to try those poles again...