Because it does not have the old provinces names! In the year 1444 there is no longer Penza, Saratov, Samara and other cities, that were not yet founded.
A city named Samar actually appears on Italian maps of XIV century. Nevertheless, Penza and Saratov are still around as I can see.
On the other hand Kanadey was founded in XVIII century and it's Tatar name is Kınadı.
Now all the names in the region are Tatarian, which adds some adds authenticity and immersion.
Saratov in Tatar is called Sarıtaw (literally "Yellow hill"), Tsaritsyn - Sarısu (Yellow water), Simbirsk should be Sember, Azov should be Azaq and Astrakhan should be spelled as Ästerxan, although a more historical name is Xacitarxan.
And you have a typo - it should be
Yar Çallı, it's actually the Tatar name for
Naberezhnye Chelny, a settlement founded in 1626. A better choice for the name of the area should probably be
Alabuğa.
And names like Lipetsk, Voronezh, Tambov, Borisoglebsk or Kuban don't sound Tatar at all.
I'm a Tatar, so I should know.
What is Etkara? Google can't find it.
In time, when Russia will begin to push Tatars away and settle the Russian plain. Civilization will come there and due to the dynamic province names system, big Russian cities will appear instead of Wild Fields. No more anachronisms!
That's a stereotype, Golden Horde had many cities, and there are some academic works about them, for example "G. A. Fyodorov-Davydov [Fedorov-Davydov] , The Culture of the Golden Horde Cities, trans. H. Bartlett Wells, Oxford, BAR International Series, 1984"
Though by XV century they were not exactly at their peak, thanks to Timur.