The point is that on Amazon, you can browse the whole collection with the long-tail as a first-class citizen. With brick-and-mortar stores the buying experience for long-tail books was clearly inferior for browsing. Sure, if I knew I wanted a particular book, I could get it -- but you couldn't browse the long-tail to explore if you didn't know exactly what you were looking for.
Every friction point in the customer experience causes potential customers to lose interest and give up on their prospective purchase. So if your potential customer has to take two actions, spread across multiple days, then all else being equal you're (hopefully obviously) going to get lower conversion/purchase rates and lower customer satisfaction than if they can impulse-buy in one action.
Every friction point in the customer experience causes potential customers to lose interest and give up on their prospective purchase. So if your potential customer has to take two actions, spread across multiple days, then all else being equal you're (hopefully obviously) going to get lower conversion/purchase rates and lower customer satisfaction than if they can impulse-buy in one action.