From what I’m seeing so far, the Web Monetization API and the Interledger protocol don’t seem all that great. Please correct me if I’m wrong, but these projects don’t easily allow for disintermediation. For example, Web Monetization requires you to create a wallet with a third-party entity to receive payments, and requires users to have an account with a third-party provider to send payments. This is not peer-to-peer, and it looks like these services will accept and transmit funds on your behalf, meaning they actually receive custody of the funds. This brings regulatory and compliance burdens for anyone who wants to setup a wallet or payment provider. Also, Web Monetization is not even a standard yet. To use it, I would have to require my users to install an extension. This is undesirable for hopefully obvious reasons, including disallowing many browsers and mobile users.
With a blockchain like Ethereum, as a developer I can create software that transmits value in a very peer-to-peer manner, right now with no browser extensions, on virtually all browsers, desktop and mobile. I don’t need to go through any third-party intermediaries to send funds, and I can create truly unhosted/non-custodial wallets for my users. The user does not have to create an account with anyone, not even with me. As a developer, I just provide the software, client-side, that allows the user to create an address and private key. They can then send cryptocurrency to that wallet, and use my application to sign and send transactions. Also with Ethereum, many stablecoins have popped up that allow users to transact essentially in USD. It gets a little more complex as you try to abstract away certain UX hindrances, but the point I’m trying to make is that blockchain protocols like Ethereum already offer simple non-custodial solutions, that don’t require intermediaries to the degree that the Web Monetization and Interledger protocols seem to require.