Tires aren't made exclusively of natural rubber, they contain synthetic polymers among other things.
Additionally, by vulcanizing the rubber, three-dimensional chemical bonds resembling those found in synthetic plastics are created to harden the material.
So the end product is not really "natural" or "rubber" anymore.
That's the point of the 15 minute city - that is, a city where everything its people need is within a 15 minute walk. People travel less and when they travel they walk or bike. The alternative, in other words, is better city design.
The heavier the vehicle the more wear on the tires, and that works the other way around too. Bicycles are so lightweight that they don't shed rubber much faster tennis shoes.
More efficient to have one central system over many small ones. Also, many forms of transportation can easily use steel wheels, such as trains and trams.
Mine doesn't have a subway/metro. A 1route regional train. We are finally making light rail, but it's very behind schedule and has cost 142 billion and still isn't very wide. The primary public transit is busses.
The last time there was a similar thread there were some links to some plant based alternatives. They seem viable but there was no investment because you guessed it, they would be more expensive than the tyres we use now.
There is Michelin’s Tweel concept but it takes a huge cost for additive manufacturing required to manufacture it since it has replicate the cushioning and dampening aspect of tires. (Or else the ride will be bumpy as hell). Only NASA uses it for the rovers and stuff coz it’s about $20k for each wheel of 4 in width.