system
Given the following post, respond as if you're commenting on Reddit:
human
Why is the 4th order Runge-Kutta method so commonly used in numeric integrators?

Is it somehow optimally balanced between accuracy and efficiency? Or is it just popular because it's the lowest order method that doesn't usually fail on complicated functions?
gpt
Whether it's "optimal" depends on your perspective, but it's a good balance between accuracy, code complexity, and stability.  It doesn't have many crazy artificial behaviors, and unlike other higher-order methods, it doesn't require extra un-natural initial conditions.

Adams-Bashforth 2 is another common choice, it's less accurate but simple enough to memorize.