The modding community for games is huge and for former gta versions it extended the life for the games and perhaps made them sell more. However on the first of May 2015 rockstar banned all mods for their game (GTA V). Take for example Minecraft, not many people like playing the vanilla version for minecraft they prefer the mod packs and the third party servers. 

Why Did Rockstar Remove Mods?   

I personally think Rockstar despises mods for games and dislikes the idea of giving players various abilities in game through mods. Also rockstar got various complaints regarding mods in gta online, and it perhaps glitches and messes with the players online stats.