Some do, like BeamNGTV, Car Pal, etc. But most don't. They either fix old outdated mods themselves (or have someone who does it for them), or have people who make private mods specifically for their channels. And then there's people like Camodo who takes private mods from BeamMP server files (WHICH IS WRONG), and Crashforce who literally steals private mods and reuploads them as his own without any credit most of the time...