Placing TODO and ASAPs in code helps ensure you don't leave any loose ends, and if you call another developer onto your feature branch allows them to get a feel for how you're getting on and how complete the code is.
Using a physical notebook distances the workload from the code and hides the fact something is incomplete from others.
A TODO graveyard can be prevented when you review the code - a developer who thinks a feature branch littered with TODO annotations is complete code is either dreaming up future use cases or failing to complete the work assigned.