This:
Honestly, pretty much all mods are stunningly good.
Obviously, I'm talking about real mods, not rips or semi-rips.
Anyhow, about your question:
- Imagine a standard player with no ambitions to race online or so, just a regular guy who likes to drive - whether it's hotlapping or against AI.
- Imagine that guy sees 2 options which would be presented somewhat nicely through the workshop: either buy a car or download a car for free
It's really not that difficult to see that for some people, not necessarily MOST or even MANY, but certainly for some people the second option would appear as the one to go with.
And this very simply would result in a financial deficit, meaning every player going for option 2 would be a loss for Kunos.