A friend had giant English rabbits that she left to roam her garden in summer. There was a ginger cat that used to sit on top of a neighbour's shed eying the rabbits up. One time it jumped down and attacked one, the other ran up, turned around and gave the cat a kick.
My friend came home to see a giant rabbit with a large ginger cat lying next to the bigger rabbit under a bit of plywood sheet. The other rabbit was under the hutch sheltering from the sun. Anyway, my friend ended up taking first the cat then the rabbit to the vets. The rabbit came home same day, the cat could not be treated beyond a bit of first aid as its owner could not be identified.
The owner was eventually but only after the vet took the decision to put it down. Apparently a very nasty broken jaw practically hanging off and other injurie meant it needed a lot of very expensive veterinary treatment. Due to suffering the cat was put down then days later handed to the upset owners identified too late to sort n out care that might have saved it.
OK a one off case but seriously, do you not think a cheap chipping is worth the expense m just in case? I think the fine is an irrelevance but the identification isn't.