Earlier quoted context omitted.
That is how all of this works. If Valve went out of business then you wouldn't have any legal right or way to get the games you purchased on Steam. If Amazon shut down Prime Video then you couldn't watch the movies you purchased on it. This is not a unique problem to Google Stadia.
You would still have your games files and be able to run them. Steam is not a rental or streaming service.
In fact I remember reading from a community representative that there are plans for this in place (not the best source but whatever https://www.reddit.com/r/Games/comments/18mzcn/i_asked_steam...)