It helps keep your schedule in tact.
I’ve found that taking notes throughout my workday is the best way to stay focused on my to-do list. So many requests come to us from so many directions–emails, phone calls, text messages–that it becomes hard not to get sucked into the busy-but-not-productive whirlwind this creates.
Try it. When you take notes, you're forced to focus. Distractions can overwhelm you without the anchor that noting gives you.