It’s the most vital part of consistent play. Wooden instruments are at their best when stored in a stable humidity environment. That’s usually between 40 and 60 RH (relative humidity). Making a guitar requires stability in the moisture standard. The recommended moisture standard and stability for storage is the same as making a guitar. If the humidity in your case falls lower than 40 or higher than 60, the geometry of the wood changes. This does all kinds of bad to your pride and joy.