If a cat is microchipped and wanders away from home and is found and handed in to a vet or animal sanctuary or to the police, they will check that it is chipped, read the number and contact the owner. If that it, the owner has remembered to register the cat with the national registry.
If you want to travel from one country to another, cats must be microchipped for you to get a pet passport for them.
My sister's one cat was found dead in a car park miles away from her home. Because the cat was chipped, she was notified what had happened to her pet, which was a relief.
Here stray cats can be rounded up by the authorities and either put down or re-homed if they are neither chipped, nor tattooed.
Both our previous cats were chipped, as we travelled with them and I fully intend to have my next pair chipped, as the law in Denmark states that anyone who wants may keep a cat that strays onto his property, if it is neither chipped, tattooed or wearing a collar with the owner's address.
Now many cats are adepts at taking their collars off, ear tattoos tend to fade badly in a couple of years, and I certainly do not want any cat of mine being claimed by someone else. This is a fairly new law, and I am afraid that cat-haters will make use of it to kill strays that are not clearly someone's pet.
Neither of our cats had any trouble with the chip and they both lived to a ripe old age.
I agree that cats kept as pets in towns are often never allowed out, but that increasesthe risk of them being unable to find their way home again if they do get out.
In the country, cats are still kept as working animals controlling mice and rats on farms, in tanneries and timber-yards. Working cats are rarely neutered so every autumn there are young strays looking for homes. You may not see them, after all they mistrust humans, but they are there.
Unfortunately, people with "second homes" in the countryside fall for a sweet kitten,, feed it while they are on holiday, and wrongly assume it can take care of itself when they leave. It can't as it hasn't learned to hunt when it should have. During lockdown people have acquired both kittens and puppies and are now realising that pets are too much work, The more responsible people hand them in to a cat and dog home, or have them put down, the others just leave them in a lay-by or a wood, where as often as not the poor animal starves to death.