I'm glad you figured out that the graph is a model, and like any good model, it picks some characteristics of reality to keep and many to leave out.

Have a look at the example of a turnstile state machine on Wikipedia: https://commons.wikimedia.org/wiki/File:Turnstile_state_mach...

The graph of that state machine suggests that you repeat the cycles indefinitely. But I have it on good authority that real world turnstiles only have a finite coin box. [citation needed] So there's some extra hidden state.