I just realized, I have spent almost NO TIME in Oklahoma. I guess it didn't interest me much.
I think the impressive landscape still attracts more attention than high level of details.
Scandinavia was a big hit despite being pretty old, and the latest
ETS2 DLC has both scenery and detail level, so it easily gets more attention than Oklahoma.
As
today’s blog post says, the feedback for the
West Balkans is very, very positive

.