Alexander might not understand this yet, but a line of big black trucks often meant dangerous people. Many regular Joes had the film mentality that if you see a line of black SUVs, you steer clear before trouble finds you.
It was all a psychological phenomenon caused by big screen showings and serialized shows that portrayed them as such. Of course, many times, that was precisely what that meant.
After all, what better vehicle to make a mobile tank out of than a suburban vehicle? Those things were already rigged to carry much more weight than they had and built with room to spare.
Bullet-proofing a vehicle like that was easy, and it would still look unassuming to the regular folk.
There was a reason politicians drove around in those, and it wasn't simply for comfort.