Your assumption that drivers of cars are going anywhere more important than where a cyclist is going is ridiculous. By your logic, someone who is driving to the local gym has more right to the road than a cyclist out for some exercise or who is going to work on a bike because they live only 5 miles from their job. The size of your vehicle does not give you a proportional right to the road.
More often than not I’ve found that excessive speed on the part of drivers is the big issue. They’re paying attention for the most part, but as we can all attest (since we all drive cars), any roadway with enough of a straightaway seems to be a license for cars to travel 20mph over whatever speed limit has been posted. Roads that should be safe enough for everyone to use become death traps for cyclists or pedestrians to travel on, even if there's a suitable shoulder, since large trucks will often use this too. And then a few months after this pattern is established, somebody tries to pass a law banning bicycles from using the road. All because people don't understand what a speed limit actually means.