Little river, it would be relative to the line and conditions but my theory is hairbrained. I did not consider that when we do get line bow it doesnt curve downward. If it was a matter of simple geometry it would affect the lure in the opposite direction, reducing the depth. I am more inclined to agree with Crankpaint after hearing his explanation. After reading thru it I can recall times where I couldnt get a lure to swim because of severe line bow. It makes it seem like you have the line taught from the water surface to the rod but the line out to the crank is actually loose and doesnt pull straight on the bait.
So I answered my own question......."Im an idiot" LOL