[aforwardslash]

And the amount of money changes the fact that the core engines are written as a one-off effort how, exactly? Updates to the scripting engine to fix play-ability issues and content updates aren't really heavy software refactoring. Sure, there are usually some actual code bugfixes on the initial releases - and more often than not - related to someone implement some really clever trick that raises an exception on some cpu. Its not like they are incrementally rewriting and extending the internal engine for a decade, as it happens eg. with a browser.

[teworks]

If you think that, you're not familiar enough with modern games as a service. Fortnite lives on the latest version of Unreal Engine, and Unreal Engine changed a lot from the initial Fortnite development until now with many new features, rewritten parts, and major refactoring of other parts. It's huge and constantly evolving, so it is similar to, i.e., browsers.