There is actually some serious thinking behind the reflective material requirement.
A number of deaths on the road have been caused by vehicles running over a person that's down from a scoot or mototrcycle in the dusk or at night, because headlights don't pick up the usual very dark materials bikers seem to prefer. Reflective patches at least give the poor victim a chance. I've seen it demonstrated by the gendarmes at night over a distance of 200 metres, and even a little reflective spot on a helmet is visible at that distance in headlights. IMHO it is one of the more sensible rules.
Don't ask me to comment about hi viz vests, cause i might throw a wobbly!