If drivers don't understand about cycle paths then they haven't read the highway code.
I doubt one in 10,000 drivers have read an updated Highway code since they passed their test. This is part of the issue with drivers, many no longer know the road laws and current advice.
Where I live we have four sections of cycle path. Three cover three quarters of a roundabout (but not the busiest junction and most dangerous section, I have only ever used it in rush hour when not going that way) and the fourth is a small thirty metre section leading to a bike ahead section at some lights.
This is despite us having some wide roads and one that would suit a cycle path perfectly (from one major housing estate into Town on a road that could easily take four lanes)
There is definitely demand for them, as evidenced by the fact that at least half the cyclists drive on pavements by default. I saw one woman at a junction signal left to cycle the wrong way up a one way street then cross the junction, hop up on a pavement and do exactly what she indicated to do. Being close to Essex driving standards are generally poor to diabolical so pavement used more often than the roads.
The Police turn a blind eye, and one PCSO rides home to his village on the pavement all the way. I suppose if our useless councils will do nothing they conclude that better to ignore it than scrape a cyclist off the pavement.