There must be reasons in Germany, France, USA, etc. for doing so. Presumably there have been mid-air collisions as well.
Not necessarily collisions. The UK system has grown about through a complex set of circumstances. Other countries will have equally complex stories but different influences ending in a different result.
This is about adopting international best procedures and practices.
Anybody who has ever been involved in any International working group to develop standards such as ICAO, ISO or ITU will tell you that the one thing theses standards aren't is "best". Inevitably the result is a poor compromise brought about by the conflicting interests of all those involved.