From my experience, I would say that there is everything, designers, people who have a hobby, visual production companies, etc.
But there are some interesting cases of people who have an idea and look for their way through the options that arise, being able to print the models gives rise to new developments in which nobody had thought before, and the author of the model less than anyone.
The same goes for other fields, video games, VR, where new ideas continually arise that are only possible because so many artists have modeled virtually all accessible reality.
That is why it is impossible to know who is going to buy your model, perhaps an idea has just occurred to him right now to use the model that is seeing someone who had no intention of buying anything.
I would say that it is important to offer original models, since it is possible that the model, by itself, generates a new idea in the user, an idea that he would not have had without seeing this or that model.