Amazon sells groceries now, too. I usually buy things from Amazon that I used to buy at Walmart. I think Amazon will be around for a long time, and Walmart's margins will shrink as competition becomes ever more fierce at the bottom end of the market.
When I need groceries and household supplies such as laundry detergent or toilet paper the last place I think of is Amazon. It seems absurd to have these things boxed, and trucked to my house in a UPS van that probably gets 5mpg when I drive right past a supermarket and a walmart every day.
Depends on what you need. You can buy olives at a supermarket olive bar for $9 a pound (wet weight), or you can buy 5 lbs for $4/lb dry weight (8 lbs wet/shipping weight, so $2.48 per lb measured equivalently) on Amazon and have them there in 2 days. There's also many goods you just can't buy in suburban/rural locations - my wife makes fabulous miso, but good luck finding 2 different kinds of seaweed and bonito flakes at your Walmart. If you don't have an Asian market in proximity Amazon is literally your only choice (and they're actually not cheap there). For pet supplies they drastically beat the selection of a Wal-Mart and drastically beat the prices of a real pet store (eg stuff like Feliway or Nature's Miracle).
Yes, for certain commonly-consumed heavy or bulky goods, i.e. anything that's either mostly air (like toilet paper) or mostly liquid (like detergent) they aren't your best choice. That's not all goods by any means.
Also you're comparing the mileage of a bus (the UPS truck) to a passenger vehicle. The UPS truck is delivering goods for a hundred other people on his run today, the gas spent transporting your package is an absolutely insignificant fraction of that. If you're really worried about ~my carbon emissions~ then you should really be thinking about ditching that car and getting yourself to work on one of those 5 mpg busses.
In Western Europe, grocery delivery is very common and supermarkets are struggling to scale fast enough. There is a stream of liveried delivery vans along my road every day, many more than all couriers combined.
In fact where I live Tesco recently raised their free-delivery minimum order threshold to try to encourage people to place larger, pre-planned orders.
You have to live in one of the selected areas for Amazon Fresh. I have addresses in three different states in my Amazon address book and none of them qualify.
Most of the stuff that you'd buy at a real-life grocery store doesn't make sense to order shipped from Amazon. Amazon as a replacement for WalMart only makes sense if you can wait a few hours for delivery and live in one of the selected areas for Fresh.
