If we don't teach our children how to write with their hands (that is not the same as teaching particular styles of artistic handwriting as an art form) then if we ever go over entirely to typing everything onto screens we would be completely vulnerable if some unforeseeable catastophe were to wipe out all electronic technology. Since almost all information and records is now in digital form, that would leave us in a state similar to illiterate peasants, with no internet, TV, radio, or even newspapers.
We would all have to learn very fast how to communicate with one another at a distance by scribbling a note, putting it in a cover, adding the name and address of the person we would like to receive it, and how the courier will be able to find that town, that street, that house and that person - and we would have to hope that they are able to read the rough scratches of the name and address so that it gets where it is meant to go, and that the recipient also can decipher what we meant to tell them.
Already, many people can't do cursive "joined-up" writing, only printing, which takes longer to do because it is one letter at a time, all stops and starts. Many can't read cursive writing either.