Bingo,I think people forget Valve went out of their way to make their profit margin razor thin, or at a slight loss because they know the benefit of having a device that basically assures a new paying user will be added in their Steam ecosystem. It’s based on Nintendo’s walled garden philosophy after all, just refined really well on PC.
It’s not a walled garden though, Valve made no attempts to lock anything down. You can install something like Heroic Game Launcher on the Steam Deck and play Epic Game Store or GOG games too.
While this is true and works out that way, it’s either put in a bit of work to get a game to run (I have epic games borderlands 2 handsome Jack collection and it crashes a lot on me) or use the store that has all the games and controller settings set up specifically to the deck. Having the option is great, but using steam is still easiest and makes any deck owners default purchase store choice for a game as steam. To the point where if I had to pay $25 for a game on steam vs $20 on epic or any other, I’d just go ahead and get the steam version if I intended to play it on my deck.
Why do you say that? Heroic games launcher already exist on Flathub and is super easy to use