What you are missing is that every time we widen roads to allow more car throughput we are making every other type of transit and mobility less attractive. Busy streets with big parking lots are unpleasant to walk or bike along, so people just drive to their destinations instead, which makes the street even busier, louder, and smellier starts this cycle all over again. Every time a road is widened or a new parking lot is added the city also becomes less dense, making getting anywhere useful more time consuming. Drivers have to spend longer on the road to get where they want to go, public transit gets more expensive as routes get longer, and walking and biking quickly become too time consuming. There is just a maximum density that cars can support which works totally fine for suburbs but breaks down in denser cities. Personally I think Park and Ride programs are the most reasonable compromise.
People always seem to forget the bus takes advantage of having multiple travel lanes and faster intersection clearance too. City of LA is starting to take advantage of their wide roads and put in bus only lanes, something they could easily do with some paint since the pavement already exists.
