It’s because refs and linesmen are human and make errors when making split-second decisions using only the naked eye and their judgement, so allowing it to play out enables the use of VAR to confirm or reverse their decision. The rozzers dont have to make such judgement; they use calibrated speed cameras.
Besides, they don’t call it when it happens. If you get flashed doing 80, no one stops you and you’re allowed to carry on doing 80, despite the fact that it’s objectively less safe than going 70.
Righty o, thanks, clearly the analagy doesn't work..