Why did Royal Navy ships use Exocet and Harpoon instead of Sea Eagle?
Short answerExocet and then Harpoon were already available, so adopting them avoided paying to fit Sea Eagle for shipboard use.
NotesExocet was available when the Royal Navy needed a ship-launched anti-ship missile, and Harpoon subsequently offered another established option. Fitting Sea Eagle to ships would have required additional spending. The explanation centres on avoiding that integration cost by buying an available weapon.