Of course, plantings required water and maintenance... so were allowed to die. No, were allowed to die in patches and then even the hardy still-living plants were rooted out to be concreted over.
There was a public outcry. So, reluctantly, the highway folks agreed to try to grow something. As long as it could be completely ignored, of course.
Today, there is a thin band of native grasses running down the center of the expressway.
Yesterday, stuck in traffic, with nothing but metal and concrete as far as my eye could see, I noticed that these fragile looking yet tough native grasses were swaying and dancing in an elusive breeze only they could feel, their delicate seed heads nodding. The light falling into this man-made canyon lit them in the way sun sometimes catches a spiderweb... suddenly they were much more real than the legion of cars and trucks surrounding them.
Public domain photo
I noticed that on a concrete sidewall or embankment nearby, there was a seepage through the concrete. A little ancient spring was still weeping - regardless of highway designers - and at the foot of this trickle, a tiny willow sapling grew from a crack in the road's shoulder.
Nature finds ways.