I see it as am upgrade as layered security is the name of the game. Sure you can have a wall but if you look at how many people you may need to have stationed there this provides it and also can support infrared and other systems to help provide a further buffer space and capabilities.
“layered security is the name of the game.”
With technology, we can see for miles into Mexico and the USA, creating huge areas for detection and tracking.
Barrier needs to be monitored too. Any obstacle not under observation, is vulnerable to counter-obstacle tactics.