Checking off tasks on your To Do list is a gratifying feeling, an acknowledgement that your making progress. But is it? Or are these tasks just nice to haves? The illusion of being busy is that you are being productive by completing all of these little assignments.
Deep work on the other hand doesn't come off as productive. I spent three hours trying to figure out a book title yesterday and while I made progress, I didn't check off any boxes.
Patiently committing to deep work has a long term compounding.