Welcome. Production numbers can explain a lot. There are more Martins and Gibsons in the marketplace than Guilds so it stands to reason they would be less represented at a vintage dealer that is not specializing. There is also a perception issue. People who have little or no experience with Guilds tend to underrate them. People who have to deal with a market that underrates them may choose to stock something with better profit potential. While Nashville may be a music capital of the world there are not a lot of Guilds on stage which means less interest in Guilds and fewer Guilds in the local market.
The folks at Carter may think that Guilds are among the finest instruments in the world but Carter is a store, not a museum, so they can't tie up too capital in instruments that won't sell quickly in their market.
Or it could be that Carter just cant keep them in stock and they sell within hours of arrival