I noticed when I started giving English conversation help that some people of other countries seemed to see English as a hobby. I live in the United States. That was just my observation. People can have different hobbies and it seemed like English was their hobby. Yes, people can study English for a particular purpose such as work, but also some people just want to challenge themselves to learn another language.
There are those of us on our planet and in all our countries that are happy just living where they live and speaking the language they learned originally from their parents. But there are all kinds of people on earth. Some people are adventurous and some people are content with their own way of thinking and existing. So, some people have an actual purpose in learning the new language and other people think it's cool to know Russian or know English or know Polish or Spanish or Chinese or Japanese or any language we have here on our planet.
As for the Russian teachers teaching Russian to non-native speakers of Russian, maybe it seems necessary for them to speak English at first if they are teaching an English speaking person. I will use an English expression here in how I say this, but, I think we people are "wired for" the language of our native country. By wired for, I mean all the electrical impulses and all the neurons are set up in our brains for the grammar patterns of the language we learn as babies. I believe that when we learn a new language we have to give our brains time to "re-wire" and for our brains to set up new neural pathways. So, the Russian teacher starts out speaking English to the English speaking student.
I probably have other thoughts on this, but this is it for now.