I do think the problem is from business concerns, though, and are a clear predictor that MCP will fail. Coming out of the dotcom bubble those left standing wanted to build moats and walls, not APIs that any third party could easily discover and use. The need for REST only shows up when a new player makes a move to effectively gobble up the role of being the gate keeper to the internet. With scale other companies will follow, but begrudgingly and only for a short while.