This has been in the eye of retailers for a long time (such as the bar code scanner guns some stores let shoppers use) in part because it makes it very easy for shoppers to (over)spend. Retailers are always looking to eliminate barriers to customers purchasing things. Amazon has a few convenient innovations that make shopping faster: one click purchases, subscription services, the dash button, and possibly one day a grab-n-go grocery. This post doesn't intend to demonize Amazon, these are all innovations that make shopping easier, but I think it's good financially for customers to be cognizant of how this convenience impacts behavior.