In traditional mixing, noise is the enemy. In the world, noise is the reverb. High-quality vintage libraries for Kontakt include pre-amp hiss, needle drops, and room tone. Because Kontakt allows for round-robin sampling (different samples for the same note), the noise never loops artificially; it breathes like a living room recording from 1972.
Beyond the specific "Vintage X" library, several other high-quality vintage collections are available for Native Instruments' Kontakt Factory Library 2 (Vintage Collection) vintage x kontakt