I would imagine it has to do with Rick not wanting his work to be associated with , pardon the expression,"Lesser Quality Puppets", i know if it was my designs,and my characters that were being dublictaed. i wouldnt want puppets that are not of the quality i provide to be associated with my work in anyway.
im sure Rick, and other designers feel the same way, we have all seen the less than stellar Rental Audrey Two puppets, some are great , but some are really poorly made.its just a way to safe guard an artist's reputaion,
this is not in any way a slam against LapRat(who builds great puppets!) or anyone else building puppets for local shows, just a generalization.