Another factor is the increased importance of software part of the product, and how that changes via updates that can make a manual outdated. Or at least a printed manual, so if they're doing updates to product launch it might not match what a customer gets straight out of the box or any later production runs where new firmware is included. It would be somewhat mitigated if there was an onus to keep online/downloadable manuals updated alongside the software. I know my motherboard BIOS no longer matches the manual, but even then most descriptions are so simple they do nothing more than list the options with no explanation.