Game devs specialize in writing code that gets displayed on a GUI. They also have to learn how to do scripting and some decision tree stuff for AI, but from day 1, they're writing for a GUI. Plus, game engines contain a tremendous amount of code that makes it very fast to make GUI. That game engine is huge and complicated and you have to spend a bunch of timing learning how the hell it all works. Software devs outside of the games industry haven't done that, and it would increase the size of a small and simple script from 200 lines of code and a few kilobytes to thousands of lines of code and multiple megabytes or gigabytes.