Why do ibooks store samples download but not sync?

Related to this, when I restored from an iPad backup, all my iBook Samples (about 130) disappeared. So unless there is a work-around, I have to try to remember which 130 iBook Samples I downloaded, redownload one-by-one, and realize if I ever have to restore from a backup, I lose them all again.

Also, all the PDFs I added also disappeared--amazing.

Apple, this is crazy. Make iCloud store ALL our downloads. When we backup, store ALL our iBooks, including Samples and PDFs, and include them in the restore.

I erased a sample from iBooks in my Mac and the confirmation dialog reads:

Are you sure you want to delete the copy of this book from your Mac? A copy will remain in iCloud, and you can download it again later.

This is entirely not true, samples are not synchronized across devices. This is either a flaw or an incomplete feature.

I have this same problem as well. I download samples on my computer, then go to read them on my iPad and nothing shows up. I can't believe they haven't updated this by now.

Indeed, here we are are well over a year later (and 3 years since the original post) and this still is unresolved. Pathetic.