This 'safety in numbers' notion is a victim-based cycling safety ideology based on the flawed premise that the roads are currently unsafe for cyclists and that only motorists can change the cycling safety status quo. This is not the case. Sure, as with any mode of transport, there are deaths and injuries that happen while cycling. But about half of these occur due to poor cycling practices - most often through faulty lane positioning. But even with all the bad road safety practices of cyclists and motorists alike, cycling is still very safe. the lifetime risk of dying on a bike is something like 1 in 140. Motoring has a much higher risk, at 1 in 75.
So I don't buy this 'safety in numbers' BS. It places cyclist safety purely in the hands of drivers, making us out to be passive victims. And even if it's true that more cyclists make the road safer, we have yet to see an increase in cycling that would make a big difference. A much bigger difference can be made by educating cyclists in terms of lane positioning and other safe cycling practices that put us in charge of our own safety.