I have books that link to online content. I've had one that had printable workbook that that no longer worked because the site had disappeared.
Are you going pay the extra money to the developers to keep the servers running? What will people choose, the 5 year support for game that might never play again, or the forever support? Game companies will raise prices, by a lot, if forced to maintain or release games.
The web archive kind of solves this problem.
Beyond that, I think the authors of your books are idiots for not making whatever content they have online not just a bundled part of the book (throw in a CD or thumb drive or whatever, not my problem. Solve it however you want. Just™ actually solve it). I've had the same happen with a quiz book I found, which had the answers online, with just a QR code in the book, which then lead to a 404 page. They could have just printed a few extra pages of answers in the back, but they didn't, and I mock them for it. They're fucking morons. Thankfully quiz questions tend to be easily googleable.
> Are you going pay the extra money to the developers to keep the servers running?
No, because you don't need to do that to have a playable game.
> Game companies will raise prices, by a lot, if forced to maintain or release games.
Good thing they don't need to do that then.