Why hasn’t peer-to-peer money transfer seen widespread adoption?

This is such a powerful question, the answer is a long one, highly opinionated and is still being written.

I'm summarize in a bullet form as to some of the points that prevent a global, frictionless, interoperable P2P money transfers.

• MFS (Mobile Financial Services) are predominantly closed-loop ecosystems and are dominated by the mobile carrier and their partner banks. Because of the closed loop, P2P has limited tentacles to connect with other systems.
• Interoperability remains a huge issue. Not from a technical point of view, but more so from a consensus and behavior point of view.
• P2P money transfer is all about need. The need might be higher in say Ghana or Bangladesh than say in Singapore or UK. We're getting there. As all payments are P2P (strictly speaking), we will see the P2P money transfers take a bigger role in the years to come.
• Agnostic: As much of the systems are closed loop, they do not offer users products and solutions that are agnostic to the bank, carrier and the mobile handset.
• Mobile payments are just taking off, we're still cruising down the runway. Expect more traction in the days to come.
• Regulations keep much of the systems separate.
• Dominance of existing players
• Costs - if P2P money transfers becomes really cheap, which it will, existing players don't like this idea, until they can dominate the space.
• Monopolistic payment systems. Open access is not provided for.
• FUD (Fear, Uncertainty and Doubt) prevails with many financial regulators.
• Micro-transactions are still not available in P2P money transfers like they ought to be.