Valve make no profit on the consoles themselves right? And if the steam deck profit model of making their money off of games applies to games bought on any handheld, then why not let the other companies have the higher end market and all the research and development costs that making a new console needs. Especially because each new generation would need a refresh to stay on top.(more r and d costs) So why wouldnt valve just keep making their current steam deck that runs stuff well enough for them to keep selling games.
Valve is wise to not fall into the hardware rat race, which is the only differentiation that competitors can bring to the table at the moment. They have the pole position in the market and are defining the handheld PC category by focusing on customer experience, not by trying pump power into the device.