Earlier quoted context omitted.
That sort of rule of thumb works fine with an abled bodied sober and alert adult, but throw in someone with a disability, an elderly person, a toddler, and suddenly it makes far more sense to have the bike/moped on the road and just offer the gutter at the very least for a bike lane. A road bike can kill a toddler.
Usually the way it works here is if a rider sees a kid or older person then they will slow down to walking pace and only pass when it's safe. Pedestrians still have right of way, after all. I am not against dedicated roads for bikes (although depending on the city's density, they can just end up as a second sidewalk), but I also think it shouldn't be treated as a prerequisite for developing a bike culture.
If bicyclists want this mode of transportation to be taken seriously, they need to start self-policing in a major way. So far I'm seeing not even a hint of that.