This map shows that most of Russia has no World Cup stadium nearby, especially the central and eastern regions.
Why is that?
This is due to the population density of Russia. It makes sense that the World Cup matches are taking place in the most inhabited parts of the country rather than in rural regions. The map below shows the number of people per squared kilometers in federal subjects of Russia:
Source: Wikipedia article on the population density of Russian subjects (In Russian).
The same thing happened during the World Cup 2014 in Brazil. Most of the World Cup matches were played in the densely inhabited coastal regions of Brazil rather than much less inhabited Amazon basin. Here is the map of Brazilian states by population density (number of people per sq.km.):
And here is the location of the stadiums during the 2014 World Cup in Brazil. As you can see the location of the sporting venues pretty much corresponds to the population density of the country:
All of the stadium venues are in or just near European Russia to keep travel time manageable.
Russia proposed the following host cities: Kaliningrad, Kazan, Krasnodar, Moscow, Nizhny Novgorod, Rostov-on-Don, Saint Petersburg, Samara, Saransk, Sochi, Volgograd, Yaroslavl, and Yekaterinburg. All the cities are in or just outside European Russia to reduce travel time for the teams in the huge country. The bid evaluation report stated: "The Russian bid proposes 13 host cities and 16 stadiums, thus exceeding FIFA's minimum requirement. Three of the 16 stadiums would be renovated, and 13 would be newly constructed."
The references given in the Wikipedia article are:
The venues pretty accurately represent where people actually live in Russia. I can't find a map with appropriate licensing which I can upload here, but there are some good maps in this Quora question.