Handwriting is unique to every individual. When you write with your hands you express your uniqueness. Thus it is a way of expression.
When we type we still have a choice to format the font etc to make the writing look unique but that is limited to some changes.
Thus when we are handwriting lesser and lesser we are loosing expression of our uniqueness.
The desire to be recognized as unique needs to be still satisfied and thus we need to do different things to express our uniqueness.
Very soon it will be a common practice to write with the hands for the purpose of therapy instead of need.
We don't need to walk miles now a days but then doctor tells us to walk to reduce the chances of diseases. Similarly doctors or psychology experts might ask us to write with our hands to express ourselves and email mentally healthy.