Britain developed their program as a way of holding onto superpower status. France developed their out of concerns that the US would tire of its NATO security obligations and leave Europe -- they wanted a force that could if not destroy the USSR, make it too expensive for the Soviets to attack. In a remark attributed to De Gaulle:
Within ten years, we shall have the means to kill 80 million Russians. I truly believe that one does not light-heartedly attack people who are able to kill 80 million Russians, even if one can kill 800 million French, that is if there were 800 million French
So the question becomes, why not remove the rest. An empty gesture maybe? Yes, but the weapons were there to protect Western Europe from the Soviet Union. Today, that enemy no longer exists and much of what was the Warsaw Pact is not part of NATO.
In any event, Europe will not truly be "nuclear free". France and Britain will continue to maintain nuclear forces, and though one could imagine Britain giving up theirs, I would find it hard to imagine France doing the same. But considering the changes in Europe since 1990, maybe this could be a coda or exclamation point noting that the times have changed.