I disagree. GOG’s main use case for me was rescuing old games from the dustheap of history. Before they came along, there were decades worth of games you pretty much couldn’t buy anymore - there were occasionally reissues or compilations of some of the big names, but even those would go back out of print. And you certainly couldn’t get any of those things in a convenient digital package. At least, not legally.
With digitally released games, anywhere that’s ever sold it generally just keeps on selling it. I’m not saying nothing ever disappears, but when it does these days, odds are it’s either been delisted in favor of a remaster, or they licensed something (music, guns, cars, etc) with an expiration date on that license that they didn’t want to or couldn’t renew. And GOG isn’t in any better position to deal with either of those things than any other store.