That's not even mentioning the network effect, where a service has to have enough adoption or demand to "force" other merchants to accept it
On top of that, you could fill a large book with descriptions of esoteric con jobs that only work on PayPal.
Elon builds rockets because of a well-timed exit, followed by lots of hard work and success building Tesla.
I would almost always prefer to click “pay with PayPal” than start some new account or fill in details on a given vendors site.
I would go so far as to say that if large enough retailers who already have storefronts were savvy enough, PayPal could make Amazon obsolete.
I know how returns work with Amazon. If I buy directly, are they going to give me the run around if there's a problem?
The result is exactly as you'd expect: the items sold by third party sellers on amazon have a large markup just to produce break-even margins. Source: my wife, who ran a business including third-party selling on Amazon for a while.
This is another hidden benefit of shopping on Amazon: they see my (egregiously long) shopping history. I'm sure they have some risk profile on me that suggests I'm not buying and returning a bunch of stuff to rip off sellers.
If I say something some pack of kids underwear is the wrong size, or a $15 LED light didn't arrive, or a pair of boots needs to get exchanged, it's dealt with in maybe 60 seconds of clicking on their site.
My guess is that people buying high-end headphones are just not comfortable with such setup.
I bought a product from a seller on their website once, but mistakenly ordered the wrong colour. Upon reaching out to them, I was told I had to ship it back myself (at a multiple of the item's cost), or buy a new one.
Meanwhile the product was listed on Amazon for the same price. Did I also mention that when I ordered the product initially, it came from an Amazon facility? Why does the seller get to benefit from Amazon's logistics but I get stiffed on the return?
There is always the issue of how well the integration performs. It is not uncommon for merchants software to get confused in the process and ship your order to the billing address or for other things to go wrong. When that happens, you now have to deal with customer service of varying quality.
In most cases, the purchase decision is easier for me to make on Amazon than anywhere else. I've been a customer since almost the first days and while I can count a lot of minor irritations, there isn't anything better.
With more and more adoption of ApplePay and GooglePay to power the checkout experience this advantage might away..
But most sites simply tack it on at the end as a payment option and ask for an account, address, etc beforehand.