I'm nearly always on foot. Perhaps it's just because I'm also an arborist and I'm hard wired to see trees and avoid places that don't have them?
The token tree thing is a problem. Daisy Barrington was part of webinar on the topic as part of the Arboricultural Associations webinar series [0]. Rarely do the species planted get based on local ecology and or have a solid aftercare plan. They're normally chosen for immediate aesthetic look (Paper / Himalayan birch being the most common) rather than how they'd exist over time.
In short birch being a pioneer species is short lived (80 years), grows fast towards light and dislikes being pruned. Where as oaks, norway maple, London planes ( some of which are "climax species") etc live for longer, grow slower and respond to pruning better, support local ecology better and some don't mind the pollution of an urban environment so much.
I would say they are pretty well distributed through places where people actually tend to live. I live in a pretty average residential area in zone 3 and not only are there nice parks nearby but there are plenty of trees. London is of course massive so I can't say it's the same everywhere but most residential areas I've visited have been quite green. The City and West End (very much commercial/touristy areas) are the exception in my experience.