Yes, because they want you to pay for a monthly or yearly subscription and you just want to read one article and maybe never come back to their site. But if I can do a 1-click "pay 1/2 cent" to read the rest of the article that would be totally fair
That's not the only thing. It's the hassle as well.
First they want you to sign up for an account. Give a lot of personal data. Then set up a payment model, often recurring. Just to read one article? No way.
Micropayments will save some of that hassle but I don't want to have an account with every news site linked to by HN.
If the alternative to a x% chance of upselling someoone to a yearly subscription is "read one article and maybe never come back to their site" then the price that the vendor will want to charge for that article is x% of that yearly subscription. You mention 1/2 a cent in multiple comments, but that's not a realistic expectation - if the paywalled sites would offer a per-article payment, they would definitely want to charge much more than that for that single article, closer to a dollar or so. They don't offer per-article pricing because the currently paywalled sites can earn more otherwise - the micropayment challenges aren't relevant, they will not sell their goods so cheaply (as it would devalue and 'cannibalize' their main revenue) even if there was a zero-fee micropayment mechanism.
Half a cent per article is a plausible target for all the weak/cheap sources who can't possibly afford to put up a paywall right now because nobody would pay. It's not going to be used by the currently paywalled sites, their business model relies on getting a not-micro amount from each customer.
