According to a recent report from NPD, owners of the Amazon Echo (which NPD estimates is somewhere around 1.6 million units sold) are making around 50 percent of their online purchases through Amazon, which should come as no surprise to most consumers as Amazon is an online merchant first and foremost. In relation to that, most of if not all Amazon's business decisions are likely made with the goal of increasing their website sales. That's the reason why you'll see Amazon's services baked into all of their hardware. Of course, Amazon doesn't just put out products for the sole purpose of getting people to buy things from their website, but it's likely a huge chunk of the reason.
In regards to the Echo speaker, and now the rest of the family of Alexa-enabled products, Amazon seems to have an interest in furthering their IoT efforts and making things easier and more efficient for the consumer, but they also make it easier for the consumer to purchase the things they may need, and what better place to buy those products than through Amazon, which sells pretty much anything you could think of from daily household items like paper towels and detergent, to other smart home products that can tie into the Echo such as the SmartThings Hub from Samsung or the Smart Thermostat from Nest.
In addition to making around half of their online purchases through Amazon, Echo owners also started spending around 10% more following their purchase of the Echo, while purchases on Amazon's website rose about 6% following that same purchase of the speaker, which, displays that Amazon's methods of increasing sales do work. The Echo makes just about anything voice activated, and buying things simply by asking Alexa (the A.I. software that powers the Echo) to order them is certainly easier than hopping onto your smartphone, tablet, or computer, then logging into the Amazon website and doing all of that typing and clicking. Between the Echo, the 2nd Gen Echo Dot which is now $50 cheaper than before, and a potential new Fire TV Stick which would have access to Amazon's Prime service that could reel in new subscribers, Amazon's crop of hardware products could very well help the company sell even more down the line, and that could put them far above other merchants, both physical and web-based.