Large retailers rely on all sorts of psychological tricks and UI work to steer you to the most profitable transactions, some of which we have labelled Dark Patterns. Not just Amazon, not just online. All that is gone with agents. At least until they work out how to manipulate the agents as well as a person, most likely by buying control of the the popular agents before their competitors do.
Yup. Retailers sell a ton of popular goods at or below cost to attract customers knowing that they will load their cart with other high-margin items to make up for it. If you remove these upsells and other temptations then the store takes a big hit.
Sure, but that requires work on the part of Amazon to set things up so they can be tricked. That work costs time and money. Amazon may not want to do that work at all. Or they may want to ban agents until after they've done that work.
