Remember, flying from sea is more than just "getting airborne from a moving airfield".
Imagine saying to a RAF SH Squadron: There's a ship - operate from it! The art of moving, maintaining, launching, recovering, securing and any other 'ing you can think of it totally different from doing it ashore. The RN has specialist branches to deal with the unique aspects of this, so safety is assured.
To achieve the same standard of assurance, the RAF would require a Fleet Air Arm to facilitate embarkations - full circle once again!