Using reasonable enhancements to visibility on a bike is simply a means to communicate our presence more efficiently as a courtesy to other road users to make it easier for them to fulfill their obligation to be safe, in the same way turn signals, brake lights, running lights, and reflectors do on motor vehicles.
They don't provide safety, they simply enhance our efforts to ride safely.
The possibility that they may fail to achieve the desired goal doesn't entirely negate their legitimate usefulness.