Use it for rough drafts. Eventually, some pattern matcher will probably be able to convert a free-hand drawing into structured graphics. Keyboards tend to be too noisy for meetings, classes, libraries, etc. Handwriting is quiet. Some people don't type.
Some people have only one hand.
Perhaps, there is less stress on tendons from handwriting than from striking keys. On the other hand, I do not get cramped fingers from typing. We should also consider the possibility that handwriting technology will cause a shift in practices. For an idealistic example, let's say that electronic technology enables an aircraft manufacturer to rapidly disseminate information about critical pre-flight inspections. They find the cracks.