I can perfectly well understand that it might not make economic sense to give backlist titles the same kind of attention as a new release. They are often relying on OCR from scanned paper originals, and OCR is not infallible.
Some of the books will be selling in very small quantities. They are only cost-effective en masse. They can't afford to fully proofread each one because the income per book is not enough to cover the costs. And all the costs are up front, if you're releasing a big backlist.
My impression is that these books are quickly checked for errors, possibly even just a random sample, and that quite a few errors can get through. I have reported particularly bad examples back to publishers, in the past, and they usually seem to want to fix them.
If the choice is between having a few errors and not having the book at all, I'm willing to take the errors.
TBH, they'd probably be better off grabbing a pirate copy and releasing that, but I'm not sure what kind of legal can of worms that would be.
