We've always assumed that modders create their mods in order to improve the game's design and to fix the bad design decisions made by its designer. But if this is true, then why would Fallout: New Vegas lead designer design and release an unofficial balancing mod for his own game?
Fallout: New Vegas lead designer Joshua E. Sawyer explained that his mod is "mostly general balance adjustments I couldn't do for various technical/time reasons, plus some general 'make the Hardcore game harder' adjustments."
Joshua's mod introduces hundreds of changes to the game; essentially making it much harder and we suspect that Bethesda didn't want to make the game that hard out of fear of alienating casual and novice players.
Some of the most prominent changes introduced by the mod include reducing the game's level cap to 35 with all DLCs installed, reducing carry weight by two thirds, quartering player's base health and halving experience rate.