Valve hardware is niche. They have (as of 2024) less than 400 people working there, and surely most of them of Steam and… maybe some games.

I really heard nothing in their presentations and interviews to suggest they have grand aspirations of shifting 10s of millions of units. The Deck I think is considered a success, and still only moved in a few years what the Switch did in a few months.

I think their target demographic is PC gamers who are just not super enthusiastic about the endless hardware grind.