I know many people keep pointing at PS5 as the competition, but I'll throw this in:

I can buy a game on PC and play it on the go, I don't have to buy anything else.

The Steam Deck+a PC places Steam in a different league than the PS5 (for now).

Nintendo Switch 2 is way closer, however the games are different (I don't love Nintendo games).

Finally for those of us with a big Steam library and kids, buying a Steam machine or a Steam Deck means I will spend ZERO on games (I can confirm)