The actual issue is the fact that sending money to someone can result in untrusted code running in the middle of your code execution and even reentering it seem

The actual issue is the fact that sending money to someone can result in untrusted code running in the middle of your code execution and even reentering it seems absurd. Sending should always succeed immediately and if anything needs to be automatically triggered in response, the trigger should be executed asynchronously. A great way to immediately see the problem is, for anyone with Rust experience, to think of this as a function taking an &mut self being somehow reentered without that &mut self being passed out by the function itself.