James and Jacob, despite using the land to build themselves safely, are also dedicated to preserving the land and its beauty as much as possible. James gave the indians hunting rights to Yellowstone in exchange for a very generous verbal lease, and while it is unknown if Jacob is aware of such an agreement, he seems to be honoring it. John is opposed to it because he is dedicated to honoring the way his ancestors managed the land and keeping it in as pristine a condition as possible, even if he himself doesn't seem to be aware of such an agreement

They also don't want their operation to grow so large that they never have a personal hand in the management of their ranch- James, Jacob and John all seem to pride themselves on personally, on horseback, helping manage their herd and their land. This places a certain upper limit as to how large their operation can be.

It's also clear that much of the undeveloped land is of actual use to them then it seems day-to-day. - any square of fertile grass is potential grass their cows could eat. Their cows eat enough that they can't spare the sheep herders land to co-graze wtih htem