> Does usage of the devices lead to increased sales on Amazon.com?

Yes. We have a few Alexa's and it's helpful to reorder commodities with your voice as you run out of that item (batteries, tape, printer paper, etc). I just add them to my cart and check the price later, but I like it because I'll likely forget to reorder some of those things if I don't do it right away.

Apple and Samsung own our pockets with their devices (and associated platform), Amazon wants to own your counter top.