Edinburgh, and possibly the other cities involved, want to chase the motorists out of the city. They want them to use public transport. I must say, Edinburgh has excellent park and ride facilities, on the edges of the city, and even three on the north side of the Queensferry Crossing, here in Fife. The incentive to use the Fife ones is horrendous queues on the QFC and unobstructed access for buses, via bus lanes and the old Forth Road Bridge, right to the city.
Along with the severe Low Emission Zone the Scottish government has legislated for, and the widespread use of it Edinburgh intends to bring in, public transport will be it as far as travellers to Edinburgh are concerned!
https://www.bbc.co.uk/news/uk-scotland-scotland-politics-49999555