It is because it is a cultural thing. We have cycle lanes for bikes in New Zealand yet we can't take our bikes on the highway. If they can put cycle lanes on the roads around the city of Christchurch, where I live, then they can paint a white line on the side of the highway for cyclists. I save lots of money cycling everywhere in the cycle lane, and save lots of money in fuel costs. I have two carriers and boxes that I put all my groceries and other shopping in. You'd think they'd be encouraging cyclists instead of people using their cars on the road. I travel the same speed as a car through the city. In some cases I'm faster as I don't have to queue up behind lots of other slow drivers, as only cycles are permitted in the cycle lanes.
There is no such thing as getting stuck in a traffic jam in a cycle lane because only cycles are allowd in it.