when you applied to join the Forces, did you want to be an officer? If yes - you obviously thought you had two routes, one being the normal (dare I say real) route of becoming a Lieutenant and one of becoming a WO.
Except for Army pilots, to be a Warrant Officer you have to be active duty enlisted and accepted into the program. In the Navy and Marines, you have to be at least an E-7 which means you probably have at least 10 years of service. In the Army, I think you have to be an E-5 which is at least 6 years of service.
As far as two routes, most of the Warrant Officers did not have the requirements to go straight to the officer corp upon initially joining the military. This is because the U.S. requires all "normal" officers to have four year college degrees (with a few exceptions). Many who subsequently earned their degrees while serving in an enlisted rank were than too old to apply for OCS and commissioning as a "normal" officer. Further, many who may still meet all age and education requirements to be a "normal" officer perfer the Warrant route as with their years of service, they will get more respect and responsibility as a WO for the same pay. It's a matter of pride to them.
The exception is the Army's Warrant Officer Flight Training program. The Army decided that it wanted the majority of its pilots to be specialists (pilots first). So the specialist pilots are Warrant Officers while the "normal" officers who will be company/battalion/etc. commanders are officers first and pilots second. The Army's philosphy was developed in the early Viet Nam era when they needed massive amounts of helo pilots for combat there. To this day, the Army still has more pilots than any of the other services.
Tthe USN, USMC and USAF have the philosphy of "officer first, pilot second". All USN, USMC and USAF pilots compete and are eligible to be squadron or wing commanders. Plus in the USN, senior pilots also command ships. This is why you will not see Warrant Officer pilots in those services.
BTW Argus - if there are any spelling mistakes, be sure you point them out. I realize they contribute significantly to the debate and information in this thread. After all, battles have been lost, Armies have been defeated and Warrant Officers have been killed by these significant errors.