Fraggle Rock was hardly accessible when it was on the air. It was an HBO series. I remember seeing some things at general retail (I was pretty young at the time), and that was when there was either longer turn around for retail toys or when the more accessible NBC cartoon show started up. I was really young at the time, but I could find Fraggle PVC's at KB Toys no problem. I think.
Back in the late 90's and early, maybe even mid to almost late 00's before the huge action figure crash, you really saw a resurgence of retro toy lines and merchandising. We don't have that now is the problem. Maybe Funko might license some 1980's movie toys, but stores tend to stock the toy series these things are in (Reaction figures, Pops, etc.) and not stock the licenses. That seems to be the only way to get any retro merchandising now, not releasing various toy lines, but one big one that encompasses different franchises. And when we had toy lines that were specific retro, they didn't do that well and were hard to find. Jazzwires' Hanna Barbera and Nickelodeon lines (even though the Nick line had some contemporary characters mixed in with the old schoolers) specifically.
So what does this mean for Fraggle Rock? General retail will only want a toy line of a contemporary property, especially if it's a movie. FR doesn't have a current project in the works, so no reason to launch a retro line. So the licenses winds up going to high end crap that sells online. There's no market for something retro outside of t-shirts that pop up occasionally. And FR isn't exactly the most well known Muppet property there is, while Sesame Street merchandise continues to pop up.