I'm not sure having bicycle paths is always feasible. The first reason is that building a bicycle path could take years and the problem can be solved much earlier and simpler in the way described.

Second, low-traffic roads may normally be safe enough for cyclists (traffic amount was never stated). The same issue can apply to remote roads of all sizes. Granted, it would be nice to have a bike road next to every high speed road, but for traffic in the range of 20cars/h I've seen that exactly once in my lifetime.