[j7ake]

You’re just quoting from Sutton’s reinforcement learning book, which proposes a learning algorithm with a Markov process assumption.

Markov processes are nice because they are simple objects and therefore have nice properties and solid mathematical proofs.

Many mathematical models are studied because they have nice theoretical properties and one can prove theorems about them. This should not be mistaken with an actual mechanistic explanation for complex emergent phenomena like human decisions.