Surely the real question is 'why exactly the RAF is the operator of these RC planes?'. They only operate in support of army operations, and they don't actually require pilots. Various army units already operate smaller UAVs, so the actual pilots in the AAC must surely be able to fly and maintain these, just as they do with the manned fixed-wing aircraft they own. I can't imagine anyone joining the RAF with a view to physically flying an aircraft seeing this as a good posting, whereas, I'd imagine, this would be quite an interesting job for your average squaddie.