I think Destiny is a good argument. If D1 ends, then playing starting D2 won't be the full experience. And new players can start many years into a game. D1 is also stuck on a console, while D2 is so big they removed content from it. You literally can't play the base campaign in D2, a huge part of the story is no longer there. A great game that "you had to be there" to play.

It's the extreme case but leaving games to die instead of having at least the chance for private servers is sad and a loss for everyone long term that don't get a chance to play it.