Kevin has "hit the nail on the head".

To add to that... here are some things to consider...

There are dozens of publishers in Nashville who all employ staff writers. The "big" ones (Sony/Tree, Polygram, BMG to name a few) have 100-125 writers. The smaller ones may have 10-25. And, of course, everything in between. For argument sake, let's say there are 2000 staff writers in Nashville. They are ALL good writers. Most have been in Nashville for years learning and plying their craft. They write EVERY DAY. They may turn in 2-3 songs a week to their publisher (that's what they are paid for). The publisher decides what gets demoed. (Except for the really successful writers who have made enough money to demo everything they write). Those demos sound as good as anything you hear on the radio or on CDs. They pitch those songs for a few weeks and if no one picks up on them, they move on to next week's 4000 songs. There are, literally, hundreds of thousands of GREAT songs sitting on the shelves in Nashville that no one will ever hear.

There are, perhaps, 50 guys/gals in Nashville who make BIG bucks (we're talkiing millions). The ones getting 3 or 4 cuts a year. Sometimes more. The artists (producers) keep going back to them because they know how to write hits - and that's what everyone is looking for. There are, maybe, another 150-200 writers who actually "make a living" writing (a cut here and there). The other 1800 are still looking for that first cut. There are only so many "slots" per year. If there are 100 (viable) releases a year with 12 songs apiece, that's 1200 "slots". Some percentage of those are written by the artist themselves (Brad Paisley, Keith Urban types). Those 50 "big name writers" get their share and the number of slots goes down real fast.

It can take years to "develop relationships" needed, or to "get noticed". Tony Lane knocked around Nashville for 5-6 years (writing daily, playing at writer's nights several times a week) before "the big boys picked up on him" and started writing with him. Once he "hit" he got dozens of cuts (several #1's).

Nashville publishers don't have time to "deal with" outsiders. Nor do they need to. If you're good enough to "make it" in Nashville as a writer, you're probably already there. At any one time there are (at least) another 5000 people in Nashville "trying to find their way in". Most don't stay long. Some do. A few make it. But not many.

All that being said.... there is always hope. Tom Douglas "did the Nashville thing" and then went back home (Texas, I believe). At a "pitch a publisher" night at a local songwiter's organization, he manage to "get noticed", got a #1 with Collin Raye and went on to a very successful Nashville career.

Never give up.