How are the tradeoffs meaningfully different? Imagine that, instead of passing an `Io` object around, you just had to add an `async` keyword to the function, and that was simply syntactic sugar for an implied `Io` argument, and you could use an `await` keyword as syntactic sugar to pass whatever `Io` object the caller has to the callee.
I don't see how that's not the exact same situation.
I don't see how that's not the exact same situation.