Perhaps the fact that there are currently no "UK licences", only UK-issued EASA licences...
There are. I have two licences issued by the CAA. One says 'European Union Flight Crew Licence on the header page, the other says 'United Kingdom Airline Transport Pilot's Licence''. When I converted my JAR ATPL into an EASA ATPL, I ticked the box asking if I wanted a UK Licence issued at the same time. It cost nothing extra.