It didn’t have a way to function in the event of system failure.

Steam sometimes goes down. When that happens, people can often still play their singleplayer games. If Steam had totally failed business-wise, it either would have been sold to another publisher who would maintain access, or the games would’ve been unlocked for permanent offline play.

Take a look at Stadia’s failure resolution strategy; they had to fully refund every person who bought a game there, because all purchases became completely unusable. Imagine if they’d gone a decade selling games to people and building off of their revenue, before encountering failure.