It's not a matter of who's serious or not, it's a matter of what is more attainable right now. Small steps are more achievable than massive ones. Public transportation and walkable cities are already a topic that capitalism has been fighting forever, and the amount of infrastructure that would need to change is massive. It would interrupt daily lives, close roads, probably close businesses at LEAST temporarily, and while those of us who support it would understand it's a means to an end, there is absolutely no way to get everyone on board right now. We DO have car parks right now, on private property where the companies that own them likely have the cash to spare for contractors to build solar panels. We'd have some areas of parking lots coned off while they build, and it would be a huge improvement that will be much easier to attain than the kind of overhaul needed to transform cities.