In a way, it's (probably unintentionally) training its human to use a narrower range of voice patterns (which is handy when collecting data to train a network with), similar to how we're more likely to write in sans-serif than cursive now that computers are ubiquitous.
There was an article on HN a while ago that claimed it was really ball point pens that killed cursive... the writing style and ink viscosity meant that the speed gains from writing cursive were no longer true, and instead it became slower.
It's also a great way to practice your speaking ability. Really trains your enunciation.
Amazon needs to develop a biz model for skills that makes sense though.