Streaming your games from your gaming pc to your Deck while at home also makes for better graphics and better battery. Massive difference to battery running Elden Ring natively compare to streaming it. Mostly using it for Diablo 4 myself.
Also some games just feel more right on a handheld. Turn based RPGs for example. Platformers like Celeste or Metroidvanias. Stardew Valley. Heck you can even play World of Warcraft without m+kb. There are add-ons to make binding somewhat like in FFXIV. Plus there is not sub just to play online like on other consoles. You bring all games with you. In my opinion everyone thats a PC gamer and can afford a Deck should have a one.