what is advantage of total conversion modding instead of developing a all new game?

Question

I only have a very little experience at game dev. I've done some proof of concept academic work in unreal engine for a university project.

My questions are

1. What is advantage of total conversion modding instead of developing a all new game?
2. And I also want to know a comparison of advantages and disadvantages of total conversion moddin vs developing a new game.
3. Isn't modding is harder because you don't have access to the source, documentation and doesn't know how inner works are done?
4. Why modder usually mod unreal tournament and half life?

Answer 1

1. You dont have to develop a game from the ground up, certain things can be left alone such as logic, which is major comes to mind first.
2. See above. If your trying to build a resume do some game-jams and save the projects as well as just doing little tech demos.
3. Completely depends on the game, what tools they have and their API and documentation.
4. Popular game, good modding toolsets and communitys with a well through out API and good documentation.

Your questions dont seem to have a lot of relevancy to anything?