Ming from Agents of Speech argues that teaching kids to say "I want X" in therapy doesn't work. The child's goal is just to get the item, and forcing longer phrases makes communication clunky without adding real meaning.
The purpose of I want is actually not very meaningful. The purpose of that is actually just to get what the child wants. And usually what happens during therapy is that after the child masters a single word or imitation the therapist or the parent tries to make the sentence longer to make it into I want something but the meaning of the whole thing hasn't changed although the length of the sentence has increased. So what's the point of increasing the length when the meaning is the same? You're making the whole communication more clunky and inefficient. So the purpose of the child saying I want is actually to get you to stop asking because most of the time how you got from non verbal to verbal was that you annoyed the hell out of your kid, right? A lot of times that is the case. When they say I want something it was a product of verbal imitation and they will keep on imitating until you give them what they want.
