I don’t think that in every case it is necessary down to user rejections. I can’t believe that in the netflix case users actually prefer to have to login with two post backs, one for the login, one for the password.
For example the buy now vs add to cart only on the Amazon one might have been looking at more than just how many products are sold, they might were also been trying to see if they can say reduce impulse buys that result in returns without lowering purchases that do not, in fact the reason they've kept the buy now might be because it actually reduced the return rate as people interacted less with the site and didn't buy additional items that they returned later.
https://en.wikipedia.org/wiki/Secure_Remote_Password_protoco...