Mostly off-topic:
I don’t paint with the curves, I paint with the presets, sure I can “grab a curve out of the box” very quickly that way and build a new preset on it, but when I make myself a brush I’m honing in on a curve and not jumping back and forth between very different curves (or strongly different curves).
Up to now, when I’ve found a curve that works for me, I’ve made a new preset with this curve, if I want a new preset with a specific curve I duplicated a preset holding that curve and tailor that preset to my needs. One could say I like to tinker, or I’m old-fashioned. 
Having a folder with a set of curves is not wrong, especially for people who do Krita for a living, things like this feature save a lot of time, and that time is their money. Storing your own curves in a library like this also has its charm, I’ve been sort of “playing disc jockey” with my presets so far. I think convenience features like this will be the future. Whether I can get away from my old habits I can’t say yet, but I’m supposed to be adaptive. 
Surely Krita is a community where sharing is capitalized, and this attitude of sharing is in my veins, as you can read in detail here. I also do not believe that I wrote anything else. However, in order to recognize this, the postings must be read as a whole, each in its own right.
But the existence of such a “curve library” has primarily not to do with sharing or exchanging, but with workflows and selection options, as well as the acceleration thereof. A strong argument for adding this “curve library” is to have a certain curve shape quickly available, I have handled this so far via my presets. By the way, you could say that the curves have been shared so far in the form of the presets.
Michelist