It actually is difficult to find an exercise for developing fine motor control that is as complete and as cheap as practicing handwriting.

All other exercises would need more expensive tools and after inventing a sufficient number of different patterns for other activities, that would be practically equivalent with writing a different alphabet on another medium than paper, e.g. carving wood or stone, etc.

I did not like to use handwriting for things like taking notes at school or at the university, and I switched to typewriting as soon as I could afford a computer. For work purposes I now use only typewriting.

Despite this, I am very grateful that in the first years of school I was forced to practice handwriting, even if I have abandoned decades ago the style of handwriting that I was taught.

The reason is exactly what the previous poster has said, that this practice of handwriting as a child was essential for developing the motor control that I needed later as an electronics engineer for soldering or for assembling and disassembling various miniature devices.