Reducing the number of cars (and therefore traffic) on the
  roads will benefit everybody

You seem to have a rose-tinted view of the world we live in.

  Have you ever had to commute in less-than-ideal 
  conditions? 
  Heavy snow? Sleet? Black ice? 
  Have you ever lived in places that are not 
  perfectly flat? or lived in places that 
  are hot that make bicycling unfeasible?
  Did you have sporting gear / work gear that
  you had to lug? Did you know some people have
  to fetch their own gear to work
  Did you have to take calls during transit?
  Did you know its common practice for employees
  to call into meetings during their commute and/or 
  help assist operations via conference calls?
  Have you had to shop for more than a baguette 
  or a bagel at a store? You know how cumbersome
  that gets for even a family of three? 
  Do you have the slightest clue how much casual 
  violence and crime happen on public transit?[1] 

Not to belabor the point but there simply are dozens of cases where bicycles or public transit just don't cut it. Not to mention the hygiene, personal safety (from other passengers for example) and personal space aspects involved in someone choosing a mode of transportation other than public transit or bicycling.

Ride-sharing, autonomous vehicles and emission-free vehicles should all alleviate the issues we currently face with traffic, parking and accidents.

However doing away with cars or vehicular traffic is just pollyannaish madness.

[1]

Teen robbed at gunpoint at Fruitvale, BART officer says writing a report is a 'waste of resources'

https://www.sfgate.com/local/article/bart-police-refuse-repo...