Unoccupied home detrimental to hardwood floors?

Q: Why is leaving a home unoccupied so detrimental to hardwood floors?

A: I can give you one scenario. A house has been purchased but not yet lived in. A new floor is installed under this scenario in cold weather conditions. The relative humidity in the house drops significantly. Just having people living in the house could alter this significantly. Every time we exhale, moisture is released with every breath. We flush toilets. We have a shower. We wash dishes. We cook. We do our laundry. All of this activity in the house provides some moisture to the entire structure. Without that, everything will dry out and shrink.