If you bother to build the cycling lane then differentiating it a bit more obviously from the sidewalk is not such a big expenditure. Loot at this [0] setup (just outside of Copenhagen). Simply having a few centimeters of difference in height between the 3 lanes (pedestrians, bikes, cars) makes them very obvious and a lot harder to accidentally cross them. It also allows treating the cycling lane as another traffic lane with its own road markings and everything. [1]
It doesn't feel like the extra kerb is a matter of cost as much as of "sharing" the environment. So the expectation is "there won't be too many bikes so pedestrians can just use the entire sidewalk when needed". This just leads to more cyclists trying their luck on the street with the cars which are more predictable than pedestrians.
Delivery drivers park half-in-half-out of these lanes in the city sometimes.
Otherwise, they're respected. I don't think I've ever seen someone driving in one. It seems a strange question. Do American drivers not respect the sidewalk? It's the same construction.
I think the police would come down very heavily on anyone they caught driving in the cycle lane without a very good reason. The only good reason I can think of would be to move slowly aside to allow an emergency vehicle to pass -- and the same reason would justify pulling onto the sidewalk -- although either action is still illegal.
It doesn't feel like the extra kerb is a matter of cost as much as of "sharing" the environment. So the expectation is "there won't be too many bikes so pedestrians can just use the entire sidewalk when needed". This just leads to more cyclists trying their luck on the street with the cars which are more predictable than pedestrians.
[0] https://www.google.com/maps/@55.6450742,12.4589657,3a,75y,28...
[1] https://www.google.com/maps/@55.614447,12.475333,3a,75y,294....