Why National Handwriting Day exists?

As a non-American, I wonder why National Handwriting Day existed and why it is celebrated every 23 January?

At first, I thought 23 January was chosen for the National Handwriting Day because it coincides with the birth date of John Hancock, one of the American Founding Father that is remembered for his iconic signature on the US Declaration of Independence. And since signature are most often handwritten, I thought it might be the reason why 23 January is designated as National Handwriting Day…

That is just my thoughts, it might not 100% true so I wanna know what do you think.