I don't think a peripheral would make sense because hardware just isn't that profitable on its own, and it wouldn't strengthen Valve's core business.
The only way Valve can grow its revenue is by yadda yadda yadda.
Valve makes money hand over fist. I don't think that making money is their ultimate goal. If their goal was to make better games and their logic is that this peripheral would help them make better games, then that is what they will do. They have enough money to basically do whatever they want. They are privately owned and so are not beholden to shareholders.