Attack robots are easily disabled by defense robots.
An attack robot/drone has to carry fuel/power and all its ammo to the target.
A concrete defense pillar, with the same weaponry, has none of these limitations.
Further, to disable these robots, a far simpler drone can be used.
Remember Luke taking out AT-ATs on Hoth with a cable flying around the legs? You could get a $10 drone to do that. You can get a lot of $10 drones for the price of one of these.
And those flying, delivery things? They do not work too well if they run into a brick, just hanging around in the sky. A brick, a balloon, and a $10 drone, who's only mission is to get in the way. Or you could replace the brick with a metal mesh net, or a can of spray foam.
Our biggest problem is our "inability" to defend ourselves from our own govern-cements.