I could be off here but, it's probably because alot of modders tend to add more content to the game than refining / replacing / removing things. Therefore, many people see this as "Modders" know best what players want...
Take Guppy's fire mod as an example. No doubt, a very cool addition to the game. However, as a mod, Guppy doesn't really have to deal with its balance with the rest of the game nor its performance impact on a wide range of systems. Many players will praise mod creators for ideas like this and then shake their heads at the developers for not implementing it.