Left-over land nobody wanted--no harvestable timber, etc.

Oregon alone one million acres of old growth ancient forest is on BLM land. There is some harvest, but the forests provide cover for wildlife and scope for recreation.
Other regions lack the timber resources, but logged land is being re-forested and some of the ills of the past (uncontrolled mining, grazing, logging, etc.), are being addressed.
BLM lands between forested mountains provide pathways for wildlife.

BLM administers and maintains:
4500 miles of scenic, national trails
Over 200,000 miles of fishable streams
8900 sq. mi. of lakes
300 sites for watching wildlife
55 million acres of forests, including 11 million acres with managed foresting.
Generated $6.2 billion in revenues (2009) with about half going to states and counties.

Grazing fees are set well below "market." Bundy, never having paid for it, is entitled to nothing.
Bundy would have had no complaints if he had followed the rules.