Still, how is it fair to give a car (usually one person - on average maybe up to 1.5) about 3 or 4 (in this particular case, usually even way more) times the room that cyclists and pedestrians get?
Becaus that road is not just for cars with 1.5 people on it. It is far more versatile. it could be a taxi, it could be a disabled's car, it could be a bus, it could be a van or a lorry moving otherwise impossibly heavy things around, it could be an ambulance, it could be a car with 2 or more people inside, it could be several things, not just the standard way we think about personal trasnportation and which is used to demonize it.
Personal transportation adapted to the fact that roads -had- to be large, and cars adapted to what they are now. Also, car size grows because marketing and people not giving a... let's say not caring about other things, but just wanting more.
Plus, motorized transportation has advantages that neither bicycle nor pedestrians have. It allows for carrying around things, it allows for faster traveling, it can shelter you from the weather, it makes traveling possible for pretty much everyone, one way or another. Walking is not as versatile, though it gets almost there, while and the most limited form of traveling is actually bicycles. Because there are so many reasons why you can't use a bicycle, and being a personal vehicle, it doesn't allow you to ride it if you're not also driving it.
Clearly, our societies have gone far beyond what's reasonable for motorized transportation, specifically in the personal form, with useless mass moved around, waste of fuel and room to store vehicles, but the idea of private motorized (whatever kind of motor) transportation while sheltered from the weather is, I think, one of the best developments of the last century, and bicycle is simply not as good, though it definitely is greener, cheaper and, if you're already healthy enough, healthier.
But what should count, after all, is not if we drive a car or a bike, but what our general lifestyle is. Resources are limited, yes. But what if I want to use my share on a car rather than other things?