We have suggested what you stated Cat, every time CA has placed those restrictions on MP gameplay, but unfortunately, that is another thing CA refuses to change. Not sure why they continue with this on every new release, but they do. Probably one of the bosses, who knows nothing about the game, thought it would be a "neat" idea and would make it more like a console/RTS game. Kind of like the ignorant unlockable-factions "feature" which forces you to play the regular campaign before you can play any other factions. Its an ego thing with CA and they probably paid some marketing exec. lots of money to research and come up with the idea (though it is stolen directly from some console and RTS games. :)

PS: CA has always been stubborn for no reason other than to show they can be. :)