Licensing is really nothing more nor less than CAA certification that an airfield meets basic safety standards.
UK CAA rules won't allow commercial light aircraft or motorglider training at unlicensed airfields including cross-countries, and UK MoD rules won't allow military flight testing at unlicensed airfields. Basically that's about it.
It is argued in certain quarters that it's just another unnecessary charge on the flying training industry, and that club instructors should be allowed to use their own judgement - frankly, I agree with that view.
One could understand some clubs or insurance companies insisting upon licensed airfields, but it's really only them covering their backsides - nothing more. No other country uses the same sort of airfield licensing system except Eire, so far as I know.
G