Games were meant to be installable on multiple consoles, so if they wanted reselling or giving away a game to completely disassociate the license from the seller's/giver's account, every console with that game would need to be kept online to verify this. So if there were an offline mode that disabled license-transfer features, it would have to apply as long as even one console were in this mode. This means that it would be possible for someone to put themselves into a state where they'd be permanently prevented from reselling or giving games because they don't have physical access to some console that's been put in offline mode.
There are of course further workarounds/mitigations for this problem, such as putting a (100 days?) time limit on offline mode, but they make the system even more complicated.
> This means that it would be possible for someone to put themselves into a state where they'd be permanently prevented from reselling or giving games because they don't have physical access to some console that's been put in offline mode.
This isn't really too big of a problem. Just require users to phone in and request a license transfer if they lose a console. Limit the number of times that a customer can "lose" their console without an investigation.
There are of course further workarounds/mitigations for this problem, such as putting a (100 days?) time limit on offline mode, but they make the system even more complicated.