ti sonic i must ask but have you made mods just for yourself and never realesed because there must be few it would make sence right?
Your statement is quite wrong if you ask that about me. If I do a private mod , of course I won't publish it. But that applies only for me.
About other modders I don't know. If they do private mods , that's because they wanted it. I know that some people do make conversions for money , but they always say the status of the mod , to avoid some bad surprises.
Usually if the car model comes from a manufacturer , they're not meant to be used for commercial purposes (license , copyrights and all the shit that comes out of them) but there's a huge space between these conversions and the reality , most of the time when a mod is made , it has something different from the original models such as alternate wheels, different interior , custom-made parts , logos, etc.
On top of that I don't think manufacturers will come after each modder to ask them about copyrights and so on, there are too many of them xD