Arresting, transporting, housing, arraigning, and watching the complaint being dismissed by Democratically appointed Federal Judges is also a kicker.
The city of Eugene turns into a drop kicked hornet's nest of anger. Demonstrations at the Federal Courthouse (That is expensive to control and monitor), minions of people infiltrating the closure, standing at the gates, and tormenting FS personnel at USFS stations, and many other events high in angry people and expense to deal with happen.
Think they haven't tried this? It is a headache. I haven't even mentioned how the headache called ELF is right there looking for how they can coattail into it destroying something.
They have tried to wait out activists in the woods. For years and years. Activists like living in the woods. Thousands of people give money, food, clothing, climbing gear, and high praise for the actions of forest defenders.
For every kid in a tree there is five to fifteen on the ground, some in the new forest "hides." For every group of up to sixteen people in the woods, there are hundreds of people in town supporting them.
Your idea is flawed; but I understand how someone who doesn't know what is going on in this fight would suggest it.
And this is the quick, thumbnail explanation. I could sit down and write a paper on this situation that would anger and discourage you upon reading it.
There are also several new sits going up this Spring too. Go figure.
Don't think it ends there either. Research and development of new forest defense tactics and operations orders is an ongoing thing. This is a big business that employs and keeps busy an extremely high number of folks.