Uselessness can be useful for a different context. For example, the Carolina Sandhills National Wildlife Refuge is flourishing today in part because on account of the sand it was considered agriculturally useless land that farmers struggled to do anything with during the Great Depression. So it was easy for the government to buy out the stakeholders and begin protecting and recovering that special ecosystem.

In the case of pine plantations, they are quite useful to people because they fairly passively produce a vast amount of wood that the owner of the land can sell at their leisure.

However, in the course of optimizing the pine plantations for economic benefit, the benefit to the wildlife is reduced. More densely packing the trees means that you have more wood growing in the same area rather than leaving unused space. But in doing so that means less sunlight hitting the ground. That energy goes to making more wood rather than to supporting the groundcover, and the groundgover is the more important of the two for most animals.