Importantly, comparing "ephemeral" structures - those that destroy previous states through direct hardware mutation - with persistent structures (such as all pu

Importantly, comparing "ephemeral" structures - those that destroy previous states through direct hardware mutation - with persistent structures (such as all pure data structures) - is a fraught topic. You can surely gain speed ups on real hardware directly mutating memory you know to be reusable (linear) - but proving that precondition is very hard, and we often screw it up. Persistent data is a safe default. Mutation/destruction is an optimisation.