Also not a game dev, but my understanding there is that there there's a lot of in-memory objects whose lifetimes are tied to specific game-time entities, like a frame, an NPC, the units of octtree/bsp corresponding to where the player is, etc.

Under these conditions, you do need a fair bit of dynamism, but the deallocations can generally be in big batches rather than piecemeal, so it's a good fit for slab-type systems.