This has been explained many many times. Modding the game is not the same as developing the game. Mod makers have one very specific goal to achieve and do not need to worry about any repercussions it might have. Does it bloat the game files? Does it cause lag? Does it effect any other component of the game? Does it support future content? Does it work with up-coming changes? Do these changes need to be agreed before implementation with management?
All these and more are questions which never pass through a modders head.Yes they do good work but all they do is change 1-2 lines of code and call it a day. Thats not game development - that's slapping a bandaid on. I am glad modders do their work but people need to stop making the comparison.