What would have been an interesting discussion is to look at how the retail market is actually unfolding:
https://www.bloomberg.com/graphics/2017-retail-debt/
And whether cutting out the variable costs of a cashier etc is really worth the trouble in R&D and systems.
Edit: After reading some of the responses, I wanted to add something. If we look at the linked article above, retailers are taking in loans to open more and more stores. The idea being more stores = more customers = more profit. But that is not materializing at all. The question becomes - where does the issue lie really? Are variable costs the reason? What does Amazon Go solve really?
Sure, some might say better software is the whole point of Amazon Go. But,we are not talking about a SaaS where the cost of delivery is nearly negligible - it takes nearly the same amount of real estate and fixed costs to deliver 1 or 1000 of a SaaS product. That is not true for B&M. If they want to ramp up then they will need to open more stores - that requires real estate and other fixed costs.