elcrusoe
Short answer.....politics.
Many states have their own set of peculiar rules and regulations and the UK has more than most. The UK promotes a single sky in theory, but shrinks away from even basic implementation in practice.
"talk the talk.....but not.... walk the walk" as it were. For example, if Eurocontrol is such a good idea, and so many Brits want to be in charge and dictate policy and practice in Europe, then why does NATS shy away from full Eurocontrol integration? If one set of global ATC rules is adequate for most of the aviation world then why does such a small piece of airspace covering the UK have so many differences?
Same thing comes down the food chain concerning jobs.....a rather bombastic attitude of ..."we want to be in charge of everything but we're not actually going to do it ourselves". One globally accepted ATC licence with full recognition has always been a dream.......I fear it always will be......until ICAO issue licences instead of individual states.......and all states operate to the same set of rules.