There's substantial friction for making such a purchase. A scheme sort of like flattr, where you would top up your account with a fixed 5-10$ monthly, and then simply hit a button to pay the website and unlock the content, would have much more user adoption.
It's still not going to get much adoption because you have to "top up your account."
Any viable micropayments system that wants to even have a remote chance of toppling ads has to have near zero cognitive setup cost, absolutely zero maintenance, and work out of the box on major browsers. I need to be able to push a native button on my browser that says "Pay $0.001" and know that it will work every time without my lifting a finger to keep it working. The minute you have to log in to this account, or verify that E-mail, or re-authenticate with the bank, or authorize this, or upload that, it's no longer viable.