I was simply saying that there could be more to it than you can see. What if they were sending NIPs to registered keepers of motor vehicles based on CCTV evidence at that same junction?
I'd certainly like to think that the Police would stop and deal with any transgression regardless of what type of vehicle was involved, but they don't always work like that.
Have you ever seen the random roadside checks the Police do? They randomly pull people over and check the VED, MOT, tyres, driving license, insurance, etc. I've certainly seen cars with drivers with no seatbelt on being ignored by these checkpoints, along with people driving past holding a mobile phone to their ear, etc. They don't even pull over a share of cyclists to check that the bicycle is legal w.r.t. two independent brakes and pedal reflectors if it's after dark. It's because they're targetting a particular problem at a time.