So why do we build fences around airports, military bases, nuclear plants, the WH, etc.?
Its not 1200 miles of wilderness around the WH.
Because it is cost effective to do so. There are different levels and types of fencing for military installations based on the function of the base.
If three million people were outside with shovels, ladders, ultralight aircraft, sling shot devices for drugs, we would all have to be border guards. How do you prevent packets of drugs from being launched over?