Borrowing from Wiki:
Land management of (national forests) focuses on conservation, timber harvesting, livestock grazing, watershed protection, wildlife, and recreation. Unlike national parks and other federal lands managed by the National Park Service, extraction of natural resources from national forests is permitted, and in many cases encouraged.
USFS does not exist for pristine preservation of deep wilderness. The goal of the NPS is preservation & low-impact recreation. The goal of the USFS is responsible resource exploitation.
Both goals have their place. We need both organizations. The key then is wise choices in designating the land.