Completely agree with you. I live in Montpellier, France, and we have had free public transportation for a year and a half, and it's very good. I definitely use my car less and take public transport more often.

Everyone, including people without cars, pays for the roads through taxes; it is only fair to do the same for public transport.

Society pays for cars in a lot of ways other than just taxes. Roads/highways/parking takes up tons of valuable land (opportunity costs). Cars cause a lot of medical conditions, from respiratory/cardiovascular diseases, to obesity. Cars add to climate change, which causes extreme weather events. Congestion and noise impacts health and the economy, etc. Cities all around the world would be net improved with much fewer cars.