No, they exist for motorists' convenience, as can be seen from the example. Cyclists have been brainwashed for the last 50 years to believe that riding on the regular road means instant death, that's why they stay in the bike lane even if the normal road is empty.
It sounds like you're talking about American cyclists. In Amsterdam (and maybe Copenhagen) cyclists are dominant over cars. But it would be pretty rude to ride in the car lane for any distance when a bike lane is available.
Not at all - in many recent renovations they reduce the car lanes from two-way with parking to a single one-way, making room for double wide bike lanes.
The plan is to make it so cars won’t drive through the city, but still be able to reach each spot.
