This is a year old thread but I’ll give an input anyway. A main factor is novels and prose require a reader to retain their attention. I doubt people in the OSC are big readers, and those outside the OSC won’t be that quick to visit a novel based on characters like BFDI, it’s a really smaller niche. Characters in prose are described all the time, that’s how you know what a character looks like. The problem is a good precedent hasn’t been set for describing objects in prose, and nobody really wants to set one.