A big problem with micropayments is that the transaction costs tend to dwarf the actual payment, which isn't good for the buyer or seller. I don't think it is an unsolveable problem, but there are significant network effects that would need to be overcome.
AFAIK it never pans out really. People turn out very stingy if they're faced with a decision to pay or not to pay for every article, so the revenues end up a lot lower than what the subscription model would pay.
When people are confronted with the actual cost, they tend to say no.
With a subscription, their head tells them that for 10 €/$ they get an infinite number of articles.
No, they get the articles that _you_ provide. But if _you_ provide only 50% of the interesting articles, as does every other provider, then approaching the ability to access 100% of interesting articles get very expensive. Just getting to 90% of the articles would cost 40€/$. And pushing that to 99% will cost 70€/$.