Apart from fixing glitches and errors, a number of mods also add additional material and never before released content. Picking up on this faulty premise, a number of brainy modders have worked on turning the game into what it should have been.
Some of them are even compulsory, though you can do them out of order if you wish. That’s one of the weaknesses of the game – everything is heavily linked to the main campaign, even most of the side quests that seem to be optional at first. In the case of Fallout: New Vegas, mods are more or less mandatory to keep up interest in the game after beating the campaign once. Mods and their Importance in Fallout: New Vegas