Memory for Switch games is more and more expensive, or at least I assume that's why so few physical games have come out for the Switch 2 (plus the whole "key-card" thing with no game date on the carts). With discs you could still use them to install a game, even include multiple discs if you need to. But as another poster noted, for a game that'll sell a ton like GTA6, it's all about just killing the resale market to make just that much more money.

And on a personal note, I feel we are living in a gaming golden age, so many amazing titles, especially indie ones, out there in every conceivable genre. If anything the problem is finding them, since there's so much being released these days. And I say this as someone who still also plays older games (especially 3rd, 4th, and 5th gen).