Why and How some offline single-player PC games are almost fully moddable while other are not moddable at all ?

Question

Is it strictly a developer decision to allow thier games to be moddable or not ? And how is it achieved ? Are moddable games “coded” differently than non-moddable games ?

In: 4

Answer 1

It’s like that because if the game is offline – all game files are located on your PC and you are free to change them as you wish.
When the game is multi-player, it requires it to communicate with the server, which you don’t have access to.