The Xbox processes the game.
Tablet just streams screen and sends inputs from/to Xbox.
So you don't really need an extreme tablet/phone/laptop
Im bringing my tablet/phone anywhere I'm going, so having a steamdeck would just be an extra thing to carry and worry about charging.
You can do on-screen controls that aren't bad for some games. Otherwise, Xbox controller.
The controller in the steamdeck has to kill its battery life some. 2 extra AA batteries, and I could use my Xbox controller for weeks.
I'd rather have 4x the screen size and not have to hold it the entire time while being semi-mobile. I'm not going to walk around and play on a steamdeck, maybe some do and then that's a plus on the steamdeck.
Steam deck is nice and I can see why people enjoy it. My thing is why more people don't like tablet/phone/laptop gaming and talk about the steamdeck like it's a game changer.
My tablet is basically my PC at home. I can access and do everything remotely, including gaming.