Why can't chatbots hold up a conversation with a 10-year-old?

These days, Natural Language Processing applications such as chatbots, speech recognition, and text summarization are gaining a lot of attraction. Countless companies have integrated or looking to integrate smart chatbot services to better serve customers. Researches are pushing the boundaries on improving natural interpretation accuracy in hopes that machines can one day reach and surpass human interpretation of natural languages. "Alexa, how much time is left on the pizza timer?" It's trivial for Alexa to respond to a question like that.