Most people already have Amazon account, and the lock-in effect is huge. I also have one, though I buy occasionally (few items per year max).

Recently I wanted to buy some electronics, and I found a good offer on a non-Amazon website. But when I wanted to proceed with the purchase, they asked for so many of my personal data (all of it required) that I decided I prefer to pay slightly more and buy from Amazon, than to hand my personal data to yet another third party.