For the best part of their lives, videogames have been eternal. If one fancies having a quick blast on Manic Miner, it’s possible, either through emulation or firing up the original hardware. With few exceptions, these games are rarely as good as you remember them, but the point is that it can be done.
Online has changed all that. Most games aren’t just software anymore; they’re a combination of software and services. The software will be around forever, but the services erode over time, eventually disappearing, and usually taking out the multiplayer component, which is usually the only thing people are still playing.
Steam presently has a number of critically acclaimed games that have garnered tons of negative reviews, simply because the online services that underpin them are gone. Some have even characterised the purchasing experience as fraud (although the Steam refunds system should sort that).
Personally, I don’t feel as strongly about it as that, but I’m also uneasy at the thought of games rotting because commercial interests dictate that their infrastructure is whipped from underneath them.