Because if they don't get lights they'll get blardy killed and then they'll complain. Won't they.
honestly, this evening I saw three cyclists. It was dark, raining. Lots of other cars, with headlights which are really glary in those conditions and bloody idiots cycling round with no lights on their bikes
And then the third had such an ineffectual little thing on the front, frankly it may as well not have been there.
FGS, invest in some decent lighting in your bikes.