Users do pay for those services, but not very much and not very often. There are simply too many obstacles in the way, both technological and psychological. To make it practical will require both social change and a much easier way to make small transactions. Not because it's difficult in any absolute sense, but because even the slightest practical barrier is enough to make people reconsider.
The most successful payment models now seem to be app stores and in-app purchases, which are certainly marked by convenience. You just give your credit card details once and then you can buy things with no hassle. A model like this for web content is the minimum for moving off of advertising!
More generally, though, this change is not something we can achieve unilaterally. We'd have to convince everyone else to go along with it, to choose paid services over free. Not an easy proposition at the best of times and, given the nature of the internet, not something we can force. (Fundamentally, this is actually a good thing because it means the internet can't easily be controlled, which is also why the emergence of gigantic, largely self-contained web properties like Facebook is decidedly troubling.)