As it has been pointed out - The allies spawn on the beach. With the way that realism would be set up it would be a mad dash to get off the beach, a well placed MG or sniper could wipe our guys before we got a change to move up.
St0rmy mentioned that we tried this before with playing on the omaha map. This is a great map but everyone hast to work and push together, a lot of players aren't used to this concept. This is NOT to say that players are not playing as a team - they are not MOVING like a team. It is hard to get used to and takes a lot of practice. This is what has to be used on a map like omaha and you can tell when its not being used.