With bounds checks: game crashes, meaningless error message given to the user.

Without bounds checks: I join a multiplayer lobby, and the next thing I know my computer is part of a botnet.

This isn't an imaginary fear, it has happened many times. Some examples from a brief search: https://gridinsoft.com/blogs/rce-vulnerability-in-gta-online... https://www.polygon.com/22898895/dark-souls-pvp-exploit-mult... https://security.gerhardt.link/RCE-in-Factorio/

I am not claiming all of these would've been prevented by bounds checking arrays, or even memory safety in general. The point is that security is not optional just because it's a game.