Useful technology presents like a superpower. I am drafting this paragraph on my smartphone, and clean it up on a laptop later tonight. By next week, a few thousand readers, from across the globe, will have read a version of it on their screens.
Useful technology grants you options. You, my Interlocutors, will engage with this essay with the same technological primitives. You may choose to write back. You may not. You are never bound to use your device in the same way I have.
To say some technology is useful is to say that it grants one capacity without encumbering them to use it in some particular manner.
This is the difference between technology that augments and that which productizes.
Augmentation, not productivity, is the ultimate end of technology.