Street trees are easy to justify on the basis of beauty alone.
Driving down my suburban road, I pass through a green archway with many of the trees from opposite sides of the street meeting overhead. Each time I make that trip I am refreshed. And my street is like hundreds of others locally, my experience widely shared. I might not appreciate this nearly as much but for the trees where I grew up in Rochester. Our home was on an equally shaded street but those trees, unlike today's maples, sycamores and locusts, were American elms, big vase-shaped trees with gracefully drooping branches.