Steam is still useful for providing infrastructure, like patching, order processing, dealing with many local regulations, VAT processing, tax reporting, community services…
Thus I:B is a AAA-like game so… not like a random indie game
In what parallel universe is IBS a AAA title with millions in funding and millions of people in following?
AAA-like in terms of quality. And I say like not title
Show me a game of this quality (graphics, network, physics, seamless open world true to scale…) not AAA of course