Scientists in Belgrade came up with the idea of “planting” large tanks of water and algae in places where trees can’t grow. The tanks are 10-50x more efficient than a normal tree for the space it takes up and is in general highly sustainable, even creating excellent fertilizer in the process. You can skip about halfway through the video for the actual information about them.
I woild guess because that would require you to completely tear up the bitumen and anything underneath it like pipes and wires in order to make room for the roots. Trees are pretty big things y’know and it’s not just what’s above the surface that matters. You could put a tank like this in say, a train station platform that’s raised well above the ground or on a building
Also a tub of algae isn’t going to become a health hazard if it gets sick or infested and won’t take decades to establish itself