You’ll find that if you practice a track with a car you’re intending to run there for a race, you’ll pick up on specific issues that sometimes can have a simple fix… such as the way the back end comes out too easily on a certain corner, or it doesn’t have the speed you need on the straight, and you can tune the car to compensate for weaknesses it might have had otherwise.
I’ll take it a step further and say that if you just jump straight into a race that you’ve signed up for on Tradition or Realistic Racing (without practicing first) you’re sort of doing the other drivers a disservice, as we aim for a realistic, fair race without many accidents. That becomes difficult to accomplish when some people in the field don’t know the track or how their car will drive on it.