Short answer: because chat is a shortcut to anthropomorphization in folks' brains. It's much easier to assign personality and intent to a chat than a floating head that needs to be 99.999% lifelike in order to not feel completely fake.
And when you get into frustrating misunderstanding of details you end up using a programming language anyway. Natural languages are to ambiguous to be useful for specific things. We humans can resolve the ambiguities in our minds, or think we do, based on context. I think the anthropomorphization argument hits closer to home. I feel guilty too of projecting more meaning and intelligence to a generated text and I think I'm not the only one.