[masswerk]

This seems to be an interestingly generational thing. As someone who learned to write prior to the 1990s, I may attest that the pen used to be controlled by balance and cautiously applying pressure. (Actually, you were punished in school, if you were caught holding the pen with grip.) This is also, why classic fountain pens, art pens and fine liners feature front pieces of a textureless, glossy material (because grip actually counteracted the control of a pen, if held that way).

[Edit] Somewhen in the early 2000s Wacom changed from thin and glossy to thick and rubbery pens for their tablets (i.e., from balance to grip). I'm still failing to become comfortable with those...

[Jaruzel]

I'm left-handed, and [writing] dyslexic. To be able to form any repeatable small pattern shapes with a pen (or pencil) such as letters or words, requires me to grip it with the force of an industrial press. Even then, I have to tense my hand, wrist and arm muscles just to write 'neatly'. As you can imagine, I don't ever write long essays.

Rubbery grips don't help me or hinder me, but I do tend to prefer them over hard plastic pens, not sure why.

I used to think 'Hey, we all use keyboards now, my failure to be able to write words wont be a problem anymore', but no... the world is now telling me 'tablets and pens are the future'. Not for me they are not; I have yet to find any handwriting recognition algorithm that can decipher my scrawl. In fact the lack of traction on the glass tablet screen makes my writing worse. :(

[Mz]

Several of my relatives have this sort of issue (minus being left handed). Some of them have seen some improvement by taking B vitamins and magnesium supplements, a thing that was tried due to information from a study. It isn't a cure, but it has made things more bearable.

[jhanschoo]

This shows the difference between writing with a fountain pen and writing with a ballpoint; the former requires and demands no vertical pressure, while the latter demands that the user push hard down on the paper. So penmanship in fountain pens focused on using the arm to write and using minimal vertical pressure.