A recent survey of online shoppers shows Amazon gaining share as the starting destination of choice.
Many point to the importance of being the default option on a popular operating system. For example, Apple's podcasting and mapping apps have massive market share despite not being seen as the best options in their categories because they are defaults on iOS.
But just as important are people's mental shortcuts. When I was at Amazon, we obsessed over being the "site of first resort." When it comes to search, Google is the site of first resort. When it comes to ordering a ride share, Uber is the service of first resort.
For us at Amazon, being the site of first resort for an online shopping trip was an obsession. This is why it was so critical to expand out from books to other product lines quickly. We didn't want to cement ourselves in shoppers' minds as the site of first resort for buying books but nothing else.
It's also why both Google and eBay were seen as existential threats. Both offered the potential of offering much larger selections of products than us and potentially stealing that coveted mental bookmark spot in the user's mind. If more often than not, a shopper couldn't find a product on Amazon but instead could find it on eBay or Google, slowly they'd habituate themselves to beginning their search on those services.
Of course, earning the mantle of online shopping default relies on more than selection. I don't know if Amazon offers more SKU's in its catalog than eBay and Google today, but it offers a superior customer experience end to end. Google and eBay don't handle fulfillment themselves, and post order customer service is dicey if something goes wrong. Amazon is the gold standard there, and that's part of what shoppers have come to rely on when they start their online shopping there.
A few years back I was in a wedding party, and I had to purchase a specific shirt to match the other groomsmen. I could only find it at Barney's, and the local outlet didn't offer it in my size so I ordered it from their website. The package was stolen from our apartment lobby, so I wrote Barney's customer service asking for a replacement shipment. They refused and asked me to take it up with UPS or FedEx, or whoever the shipper was. If it were Amazon, they'd have a replacement package out to me overnight on the spot, no questions asked. Needless to say, I'll never order from Barneys again, but it's amazing to think that Amazon's customer service is superior to that of even luxury retailers.
In hindsight, thinking Google might surpass us in shopping seems farfetched, but there was a time eBay had surpassed Amazon in market cap and was growing their sales and inventory in a way that inspired envy in Seattle. It turns out there was more of a ceiling on the potential of auctions as a shopping format than fixed price shopping, but in the moment, it was hard to see where that shoulder on the S-curve would be.