If the Royalty was to go so would are Military effectively as we know it. The Military is there to protect the Country and the Queens People.... hence the saying "FOR QUEEN/KING AND COUNTRY". If the Goverment had control of the Military and the Police then you would almost have no protection for the countries people. Take the recent riots in London, there was a reason the Military were not used, because turning the military against its own people would be catastrophic, who would be there to protect the people of the UK IF the Police stepped out of line. Hence why for the time being it is still controlled by the Queen. This leads nicely onto my next point
Good grief - I'm a Royalist, always have been BUT I don't buy this strange argument at all. Are you seriously suggesting that the only thing that prevents the military being deployed to our streets in a riot situation is the Queen You don't see the military deployed for riots in the US or France !