Typically simulators don't benefit much from extremely fine-grained parallelism; while you likely can simulate each entities behavior in parallel, and then step

Typically simulators don't benefit much from extremely fine-grained parallelism; while you likely can simulate each entities behavior in parallel, and then step the world, you don't have fine-grained dependencies within one step (and likely many entities computations have predictable and balanced computational costs, further simplifying parallelism). AAA games were certainly until recently renowned for their poor usage of parallelism, though perhaps there are exceptions - but remember, large scale data-parallelism akin to simulations isn't the problem; it's problematic once there are dependency cycles and/or parallelism needs to be particularly fine-grained. Finally, many games and simulators are written in clearly, clearly sub-"optimal" fashion. Games are about fun; not necessarily about extracting maximal possible performance - and compared to browsers, even to minor players like Firefox, even large games have limited usage and especially limited lifetime usage, and they're likely less sensitive to security issues too. As a result, when a game's usage of of parallelism has a few very unlikely race conditions that might not be a show-stopper - whereas it could be an exploitable flaw in browsers. All in all, it's extremely plausible that games+sims aren't quite as dramatically impacted by C++'s risks as a browser's styling engine is. It's perhaps no coincidence that the language was pretty much designed for it.