A lot of if not MOST of these avatars and assets are made by Asians, and in that part of the world, chubbiness/plus size/ anything over 120lbs is considered obese to their standards, which means a lot of asset makers don't find her attractive because of her body type. Sure there's a few exceptions, and we have as many assets for her now BECAUSE of those few exceptions.

But exceptions don't replace the norm that through out the entire world, NOT just Asian countries, skinny with big booba and no booba will always be the the preferred look over someone with Ichigo's body type

For a lot of Shop owners- what they make boils down to what seems profitable at the time, so If a base proves to be less popular, then its a risk to put in effort/time into making a product for them when its assumed it wont sell to a profitable quota. VS making something for manuka/milltina for example because so many people are seen actively using those bases in VRChat.

Another reason would be personal personal dislike of either the model or the model creator. I cant speak on personal drama if there is any, but reasons for why someone may not like her as a model could be because of her looks, proportion, functionality(For example, bad weight painting which would make it problematic for outfits), and any other number of reasons.

My personal thoughts would really be the first thing I wrote about- I do not see anyone using her in vrchat and that's not to say nobody wears her, its just a quantity thing. In these current days, I personally see more milltinas, rindos, airis, shinanos, and manukas more than any other base. So people would naturally cater more towards what the player base is using because it guarantees more sales.