Living in Switzerland there is no such thing as personalised plates. You either get what you're given by the insurance company, or you can purchase a number. The lower numbers are worth more. In Liechtenstein the police have the first few. The format is all XX nnnnn with the Kantonal abbreviation followed by numbers which are currently max. 6 digits in Zurich, e.g. ZH 123456
Having not lived in the UK for 20 years, I cannot deal with the current UK plate system. Something about year/month coded somehow, and two letters at the front, it does not compute for me as all I can remember is the old single letter (first or last) for year plus the code for first registered (which is still there?). Oddly, I still remember my dad's Ford Cortina reg. from the 70's!
Back to Swiss plates, there are a few major pluses to the system here (ignoring the non-personalisation)
1. Having plates means the car is insured. You don't get plates with the car, you are essentially 'loaned' them by the insurance company. Yes, someone can drive around with fake plates, but it does not happen too often. So in case of an accident, there is almost zero chance of the other party having no insurance.
2. You can have two cars on the same plates. All you do is move the plates from one to the other and back. Since you are only issued one set, you can only drive one car at a time! (See above about fake plates). You only pay the minimum insurance for each car, then the higher single insurance for both. Also you pay road tax for the higher value/rating only.
3. When you change cars, you tell the insurance company and the plates move over. Also, if you change insurance company completely you (can) keep the plates. So you can have them for life. I think there might be laws to prevent you selling them, and/or transferring them within the family, but not sure.