I just have one little question: why the cookie storage isn't used?

Isn't it the most usable cross-browser and easier storage engine that we can find?

Or maybe I didn't find the rela goal of this plugin?

The idea of this plugin is to not really leverage cookies. There was a cookie storage engine which was written and included in the 1.2 release of jstore, but on thinking through things with the 2.0 release, the cookie engine was removed from the specification.

This plugin is designed to leverage new technology for reliably storing more than 4k of information on the client side, which cookies do not leverage well. Additionally, the way the cookie engine was set up, it would be extremely easy for a user to accidentally corrupt the entire store of data.

If your goal is to use something that can be stored in a cookie, use the jQuery cookie plugin (which is fantastic). This plugin is more for robust web applications which need a client-side persistant store for data that the average user doesn't have direct access to. (People know how to view and clear cookies, but most aren't even aware there are client-side storage engines).

ok, thanks for this clear answer and the advice in it.