[Quoth]

Jailbroken Kindles is a tiny percentage of Kindle users. Pretty much only is done for KOReader. Also up-to-date FW usually can't be jailbroken.

I do have a jailbreak on a Kindle DX, partly out of curiosity and party to set the time, but not any other Kindle and none of the many Kindle users I know have any interest in Jailbreak or KOReader.

Also you can read a pirated book on any ereader or app. It's the DRM'ed commercially sold or library loans that take expertise to read on a different device to that intended, and that doesn't need a jailbreak either.

Jailbreaking is irrelevant to reading ebooks and the only thing that absolutely needs it is a wish to to use KOReader on a Kindle.