The UK was the first country to have an independant air force. Why would almost every other nation follow suit if it was such a bad idea?
This one has been flogged to death many times before so I'll keep it short and sweet. Navy - sea; Army - land; Air Force - air; seems to be a very sensible, efficient and logical division of responsibility to me, but government and the MoD exist to continually re-invent the wheel and fix things that aint broke!
Many of the most outspoken advocates of carving up the RAF are senior pongos and fisheads, whose understanding of air power is limited and flawed, and who are often publishing their memoirs at the same time. Tim Collins take note.