Just an odd thought:
Close rhyme schemes tend to make a song catchier. More complex or distant rhyme schemes tend to give a song a more contemplative, ballad-like character. Commercial country music producers don't want contemplation, they want cash.
A random sampling of the local pop country station over the last few days shows an overwhelming preference for close rhyme schemes, and probably 75% of them are (aa)B(cc)B - where (aa) would be an internal rhyme between two half-lines. (Sorry, don't know the academic way of notating this.)
The US country music industry is eaten up with the herd mentality. Something worked once, so everyone has to copy it to the last detail whether they understand why it worked or not. A writer selling to a particular market has to work to its specifications, even if they are artificial.
Just my cranky 2 cents.
-HM