The theory I've heard is that cyclists being on the road is only a problem when it's the exception. When it's rare, motorists aren't expecting it and are driving in a way that doesn't accommodate it.
If cycling were "the default," motorist behavior would be very different because everyone would be expecting it.
I'm even all for having no limit on watts or horsepower. If I want to haul a heavy trailer with a custom bike that draws 10kW but can't break 20 MPH, I should be allowed to do so. Having the torque to quickly get through an intersection saves lives and impatient drivers are less likely to make dangerous maneuvers if people can get out of their way quickly. Cars don't have HP limits, they have speed limits, and those same clowns who risk themselves and everyone around them for fun are always going to do what they want regardless. I feel it would be better to make speed limit laws stronger and get rid of the laws that pit pedestrians against other pedestrians over antiquated statutes.
This type of thinking, "One person might be frightened, so let's continue to make cyclists pay with their lives" is unfathomable. It's even more incomprehensible that it seems to come mostly from motorists wanting to dictate how all pedestrians 'shall obey' because the are second class citizens. "One could argue" all kinds of things without data and get nonsensical laws passed that affect other people and not themselves.
Furthermore, sidewalks already exist in vastly larger coverage of most cities, where bike lanes do not. Most places don't want to pay for bike lanes, and those that do rarely maintain them in the US. They have never run a street sweeper over the bike lanes where I live, and if they had, they would have hit the concrete spill that's been there for over 3 years and likely damage the street sweeper. It's outrageously dangerous if you don't know it is there because it is between the roadway and a turning lane, so if you get ejected in either direction you are possibly roadkill either way.
This is false, depending on the region.