If something can go out of spec 99 times out of 100 and nothing "bad" happens, you may not want a thing that makes you stop when it's out of spec.

It's not a good look, but that's often why it is done.

Same reason that militaries have strict non wartime limits on lots of their equipment, they know it can run past the norm but they also know there are risks involved, and you don't want to risk it until it's necessary.

They don’t need to even do that, just occasionally send the train past a thermal camera and look for wheels that are warmer than average.

The same reason airlines don't put airtags onto passengers suitcases: it costs a lot of money for thousands of units, plus labour and time cost - money which could be going to someones bonus (or shareholders). Also, they don't really care if your luggage gets lost, just like rail companies don't really care about this specific derailment - as long as they are making more money from the "efficiencies"

The don't want to. It increases the amount of time those cars are not hauling freight.

Nothing stops this train.

Nothing.