People who never got rid of their NES can still play their games. If it breaks, they could buy another one, or maybe even try to fix it themselves.
Once a service shuts down, you don't really have anything to keep or to revisit. If there was a Stadia-only game in the future, could you somehow get a copy and run it on local hardware to keep playing if Stadia shut down? Could you do it easily.
Super Mario Bros, Classic Tetris, etc. they still have active communities of speed-runners, tournaments, etc. It's kind of weird that something with the level of cultural impact a videogame can have could all of a sudden disappear because it doesn't exist anywhere but in a centralized space outside the control of the people who experienced it.