Early Valve coasted on the money Gabe Newell personally made as a senior Microsoft executive, so if you want to emulate that Valve then you'll need to find 8 or 9 figures in your bank account without taking any outside investments, in order to keep the company completely untainted by shareholder influence. That's not a template most founders can follow either.

There's a timeline where startup Valve went through the standard publisher funding model instead and got pressured into releasing the "finished but not very fun" 1997 cut of Half Life, rather than taking an entire extra year (an eternity in game development cycles of the era) to overhaul the whole game at their leisure.