Emma Pfaeffle, who plays Veruca Salt, talked about it once in a video (it may have been a live on, so it doesn't exist anymore, and she said that Borle chose to shave his head to save time. I think they calculated that in a 1-year run, he would have spent something like 9 full days in the hair chair to get his fair in a cap, and then the second cap over it that is mostly bald but with some hair under it (what you see sticking out under the hat). If I could link the video, I would, but I think it was live.