The microchip basically is just a device that spits out a unique number, an id. The core of doing something meaningfully then lies in the database(s) that link

The microchip basically is just a device that spits out a unique number, an id. The core of doing something meaningfully then lies in the database(s) that link this number to contact information. A huge database that like any database over time will obviously accumulate inaccuracy, out of date info and bogus data. For sure, making chips mandatory is an effective weapon against unregistered cats. Whether it also solves informing owners their animal was recovered remains to be seen. There have long been a similar databases for bicycle frame numbers in the Netherlands, where the use case is fighting theft. Despite a lots of diligent bureaucrazy the percentage of bicycles returned to rightful owners is in the single digits.