It's $50B because lots of people trust it to do something that is easy to understand and lots of the people trading have used it. The difficulty with replacing

It's $50B because lots of people trust it to do something that is easy to understand and lots of the people trading have used it. The difficulty with replacing it by something open is that you need to host it somewhere securely, and you need to make it externally visible to have 3rd parties sign stuff And you need to get all your auditing spot on so that in 5 years time you can show that 'yes, Bob did sign that contract, so can we have $... from him'; which probably means it can't be hosted by you, but needs to be something an external party can audit. And the signing process has to be simple enough that managers/lawyers/CEOs can use.