Is it because almost all of the servers is people with the demo version?

yes. that pretty much it

Wow, last time i played there was a some drifters with the full version. I had a break with this game. I went back to have some fun on the Autocross with random layouts, and now there is no more guys with full version that drifts?

You can see in serverbrowser which car is allowed by looking at the dots-matrix thing.

I dont really drift but there always seems to be some populated drift servers with XRT/LX/RAC cars.
Right now I see at least:
KaizenWorks Drift Palace
JPC TEAM DRIFT SERVER

Maybe this is interessting too:
https://www.lfs.net/forum/thread/86018