If you make it graphics only, that is possible, as the graphics don't need to be nearly as fast, but for a simulator like BeamNG, you'd need actual particles, and bypassing those means treating the environment completely differently (hear "makes it slower"). There is a reason this is not in-game yet/won't be for a while, and it's not laziness.
So you think that it’s super easy to make scratches? Read these posts: Again, hundreds of custom high res textures for every car. It’s not easy.
Well, it’ not like it shouldn’t, it can, but it would be very hard to. You’re reasoning of, “Basically every racing game has this” is because companies like EA, Sony(gran turismo) and Microsoft(Forza) are HUGE companies, with a lot of people hired to create these games. Beamng however, simply doesn’t have as many people working on the game as these major companies do. And doing that takes a lot of skilled people(not saying the beamng devs aren’t).
Don't forget that those physics engines are... "designed for the end user"... far before realism, so many of these scratches are completely random within the hit area, which I don't see devs happy with.
How do you propose these scratches to appear? They could fake scratches easily just like all other games, but they won't. They have less than 50 people working on the game and they strive for realism. To accurately simulate scratching while also calculating the physics is likely impossible on most modern high end computers.
I don't mean to say that its impossible, but we should treat it as such. Other "impossible" things have been added like traffic, but unless they have a breakthrough or miracle it probably won't happen.
Personally, I think it's possible or will be in a few years at least. I think someone should give the devs 20,000 dollars, encourage them to go to Havard or a European Ivy League school, and give them 5 or so years to figure out how to implement it. The devs could also collaborate with other game developers.