On the other hand, it may be that building later is optimal. In that case the investor is called a land speculator. The answer must be that we do not know at this moment what that better use happens to be. The plans reflect, to some extent, the notions a committee had about future developments. Their notions are frequently way off the mark.
Lumber is a resource.
Obviously, it may, in part, be man-made. Actually, though, this may be where your confusion lies. I've been wondering for a long time just where my confusion lies. The speculative motive generates a source of demand that reflects expectations of the future. At any moment in time, land may be sold at a price that reflects these expectations.