If there was a correlation between successful prosecution and wearing of a helmet and hi-viz, I could see the validity of police and others observing the cyclist was not wearing such clobber. However, there is no such connection. If cyclist is attired in this manner then the defence for the driver just does not mention this and moves on to further excuses.
I do wear hi viz pink as I do not think drivers see green or yellow. I get some abuse sometimes when in the pink but the cats driving the cars and vans do usually see me. I have a very garish orange tank top, fake fair isle from Liberty when it was closing down. I am always seen when I wear that. Drivers actually swerve into me,
Lights I am very keen on. Two folk on towpath last night on bikes without lights. Umpteen dogs and walkers very hard to spot. M night vision may be deteriorating but in case this gets blamed ever it has been amongst the highest tested night vision in the history of night vision and is coming into the high average range now. Some walkers and dogs do wear lights or put their phones on or carry a newspaper or white poly bag.