That's disingenuous. Obviously the echo is capable of far more than purchasing things from amazon. I'd guess that most echo users don't actually ever use voice purchasing.
I've never used mine for purchasing and I use it an absolute ton. Mostly for cooking and converting units so I dont have to put my fish-covered hands on my phone to calculate things. If doing things in the kitchen was the only thing I used it for it would still have been worth the investment.