I do, I've never printed one of those boats, but not everyone's interested.
If you think of it as functional/decorative categorisation first of all, obviously some people will overlap but broadly speaking I think people are interested for one or the other, then within the 'decorative' camp you can go a hell of a lot further without and I think it's more obviously reasonable to not care about designing your own models. You never wanted to design your own toys, but there's appeal in printing things not available on Amazon, unofficial merch for a film you like, or whatever.
Not to say there isn't functional stuff (which I exclusively print) on these sites, but often it won't be quite what I want, so yeah I end up in Fusion. (And typically starting from scratch eventually, because for some reason people don't share source, and working with imported STLs is hellish.)
Resin printers are HUGELY popular for people that paint miniatures and do tabletop stuff. Most of them never design characters and just buy the cad models to print.
There are several "CAD lite" systems available if you don't actually need dimensional accuracy though. There's a model boom in DnD circles around sharing 3D models, slicing them up, gluing them together, and making your own designs by basically digital kitbashing.
My friend is filling up hard drives with 3D models DMs share.
