Those asserts probably saved a lot of development costs and increased the robustness of the software, which is worth a lot more than a few percent on a benchmark.

I personally am more conservative on those things. I'll pick the fastest thing that is reliable.

Are we talking about games or medical devices here? I expect different things from them. If a medical device needs to turn off bounds checking to get results I'm concerned enough to not want to let anyone use it. If a game can get a slight performance improvement I'm all for it, who cares if it crashes, it is just a game.