For purchases where I need to type in credit card info, yes I prefer desktop over mobile anytime. But I use the Amazon app on my iPhone all the time because its just one click to purchase something. That is the driver behind this idea, if buying on mobile can become simpler than buying on the desktop, why wouldn't people do it?
I can already buy something with one click on Amazon.com from my laptop and desktop. And have been able to for some time. Adding that feature to a mobile phone will help, certainly, but that alone would not make a better shopping experience in my mind. I would still have to have that company's app, or browse their site in my mobile browser, which will always be slower than using a full fledged laptop or desktop.
I agree that if someone could make purchasing simpler on a phone than on a laptop/desktop (possibly through NFC or something) then it could be a preferable approach. But just storing credit cards isn't going to cut it in my opinion.
I think the difference here is that I'm already on my phone or iPad looking at the item in the first place. It's a pleasant experience for me to look up things that I might like, or to grab something I know we need. Oh, we're out of light bulbs? Pull out the phone, Prime them, done, don't need to think about it. It's not that it's easier on the phone/tablet over the laptop, it's that more and more those devices are becoming the first thing I go to.
