So basically it's belt and braces in case of ATC transmissions being misheard or misinterpreted with similar sounding flights in the same area at the same time? I can see the logic in that. Just seems random to those not in the industry.
Eurocontrol reportedly have a computer system that identifies potential conflicts between not only flight numbers of aircraft likely to be talking to the same centre at the same time, but also other possible sources of confusion such as frequencies, runway headings, etc.