I wonder what keeps them from cutting throught that thing?
It ain't that easy to cut even a small hole. The fine tough stainless steel mesh does not allow bolt cutters or mechanical tools to work. Oxy acetylene is not effective against stainless steel either, it's a mess. It takes a major effort to cut it.
Meanwhile, the Border Patrol, (no longer wasting its time and spreading itself out chasing hundreds of illegals over the wide open hinterland) can focus their resources on defending this fence, meaning that they can respond far more quickly to any attempts to cut it.