The flowchart on the back-end looks pretty involved, needing to publish transactions on the chain and get confirmations. For Bitcoin, that takes upwards of like 15 minutes depending on what block depth the receiving party cares about and stuff. Even foregoing that and just listening for conflicting transactions being broadcast for a few seconds, that's an annoying delay to open a page. Not to mention dealing with the UI to authorize a specific payment for every damn page on paywalled news websites