In fact doing some things on the deck is more tricky because it’s limited to installing flatpaks.
That's the advantage. A PC with a layer on top is a PC with a layer on top. It still wants you to have a mouse and keyboard. You still have to update it like a normal desktop PC.
Steam OS is controller and controller only. It's a no bullshit durable system designed to be put on a box and just leave it that way.
You can do the same things, but I'm not putting a norma lLinux box running steam under my TV.