Virtual walls can be turned off at the flip of a switch. Surveillance drones can fly around with nobody taking action on what is seen, with the ruling class claiming that they are doing something. Physical walls have to be torn down to become ineffective.
“Virtual walls “
I assume that’s a setup where any crossing of the border can be remotely detected, meaning you wouldn’t need a person every 1000 feet or so.
If this wall detects someone crossing, do you shoot them? We don’t do that. Do you capture them? If you just take them back into Mexico, why shouldn’t they try again? Holding them as captives is expensive and has moral problems.
Best and cheapest bet is to stop them from crossing with a “harmless” wall.
Of course no scheme will stop every border crossing. We only need to reduce from a flood to a trickle.